Some further thoughts / interp notes.
* Status Blocking / Accessories. By endgame, every character has 3 Accessory slots. Accessories are totally non-unique - there is nothing like Shadow / Relm's Memento Ring to my knowledge. They are also, however, storebought. Your call on if they should be legal, and if so, how they should be interpreted / what should be allowed. In game, these will probably be handy stat-boosting accessories that cover your main stat - Magic for Hope / Vanille, Strength for Snow / Fang, etc. There are also some solid HP boosters and defense boosters with things like "resist all elemental damage by 25%" or "resist physical and magical damage by 15%". I can totally see throwing all the stat boosters out for sake of sanely deciding what's expected of characters, though I'd offer some nebulous general bonus to statistics, which would have the effect of slightly flattening out the curves (Hope's HP isn't as bad with accessories taken into account, since +1000 HP for him is more noticeable than +1000 HP for say Snow).
More relevantly, there are storebought status-blockers for every negative status ailment in the game, save Doom (= instant death countdown, used only in plot fights, not by normal enemies). They all resist by 30% unupgraded, and 45% upgraded. It is orders of magnitude cheaper to upgrade these then to grab a maxed lvl. 3 weapon, mind, even if you wanted to have every status blocked for all 3 characters. They also have lvl. 2 forms if they are transmuted; these go from 40% resistance at lvl. 1 to 60% resistance at max level, but they are not storebought directly. However, the Perevoskite necessary to transmute lvl. 1 -> lvl. 2 is storebought. I personally would not allow the level 2 items, but your call. Stealing from Daetrinn's FAQ on GameFAQs:
Resist Debrave | Giant's Glove, Warlord's Glove
Resist Defaith | Glass Buckle, Tekite Buckle
Resist Deprotect| Metal Armband, Ceramic Armband
Resist Deshell | Serenity Sachet, Safeguard Sachet
Resist Slow | Glass Orb, Dragonfly Orb
Resist Poison | Star Pendant, Starfall Pendant
Resist Imperil | Pearl Necklace, Gemstone Necklace
Resist Curse | Warding Talisman, Hexbane Talisman
Resist Pain | Pain Dampener, Pain Deflector
Resist Fog | White Cape, Effulgent Cape
Resist Daze | Rainbow Anklet, Moonbow Anklet
Resist Death | Cherub's Crown, Seraph's Crown
Debrave is -STR, Defaith is -MAG, Deprotect is -PDEF, Deshell is -MDEF, Slow is the usual, Poison is the usual (FF13 poison is not very scary, FWIW), Imperil reduces elemental resistance by one level (usually equal to double damage - neutral becomes double, halved becomes neutral), Curse is "you are easier to stun-lock and make you lose actions from being attacked", Pain is "physical silence = no physical-based abilities, including the base Attack", Fog is Silence (no magic-based abilities), Daze is Stun/Stop, Death is Death.
You can stack the same equip multiple times in-game, or for that matter stacking these with a Ribbon (="resist all status ailments by X%").
EDIT: See Tal's note below.
Stacking works multiplicatively, so putting three 30% accessories on is 1-0.7*0.7*0.7 = 65% resistance. (Three 60% accessories is 93% resistance.
And three 45% accessories would be 83% resistance to the status ailment.
If you are lenient and allow accessories to be reserved for status-blockers, FF13 characters can mostly stop a single status ailment of their choice. Of course, FF13 characters are in more trouble if they have to defend against multiple potential statuses. Personally, I would assess a nebulous "stat penalty" to FF13 characters who are stripping what, in normal gameplay, would be stat boosters for status resistance. (I do the same for, say, Shadow Hearts 2, where that Leonardo's Bear is replacing a Defense-boosting Belt.)
* Allowable Weapons / Accessories. I don't want to torment Talaysen and make him re-run the numbers yet again, but I definitely prefer the upgraded lvl. 2 weapon statistics to the upgraded lvl. 3 statistics. To get the materials needed to transmute lvl. 3 weapons means taking on aftergame powered monsters, so it feels aftergamey. (I took on a mere A-class sidequest and got my ass kicked but was still able to beat the final boss, and getting Trapozohedrons requires beating up Adamantoises and the like.) In fact, just as a general rule, I think I'd even prefer max upgraded *level 1* weapons. It's tough to draw a sensible line, but considering the large numbers of weapon options characters have, I can sorta see upgrading all your level 1 options to the max, but getting even all your level 2 options for 3 characters by normal endgame would be insanely expensive. I think saying "if it's storebought, it's legit, but no transmutation" works well as a semi-arbitrary dividing line for power. Continuing the above note on accessories, I'd cap the allowable status blockers at upgraded lvl. 1 equipment, so Cherub's Crowns are fine but not Seraph's Crowns. (Side note: In game, I took Tonfa's advice and didn't bother upgrading my weapons ever, so I ended the game with unupgraded lvl. 1 gear. Upgraded my accessories instead, which gives you party flexibility - switch in whoever you like but give them the sweet accessories. Make of that what you will.)
* Allowable Paradigms. I am against allowing the secondary roles.
-- In the DL, letting everybody have all roles reduces uniqueness. We don't let FFX characters wander outside their segment of the sphere grid despite Teleport Spheres making it doable in-game, so we should apply the same standard here.
-- It's not a good deal in-game, unless you're power leveling and capped with nothing else to spend the CP on. The costs on the secondary role abilities is very, very expensive and quite inefficient compared to the primary roles. For example, Lightning has HP +180 for 10000 CP in her lvl. 9 Commando Crystarium, a less efficient HP +150 for 12000, and a very inefficient HP +80 for 18000. Yet even that horrible +80 for 18000 (225 CP per HP) shines like a diamond compared to Lightning's off-class HP +10 for 3000 CP in Sentinel (300 CP for 1 HP). And Sentinel is the class with the best HP growth, and the rates get EVEN WORSE after that. When I finished the game, I hadn't finished getting all the stat boosts in my primary roles for each character, so yeah. Getting up to lvl. 3 in each off-class strikes me as taking an overly late gameish average, although I will grant this is probably plausible if you sidequested heavily in Chapter 11 (I didn't).
-- Since you are restricted to just 6 paradigm sets anyway, it'd be quite difficult to slip off-classes in anyway. I know that there have been many times I wished I could switch to a different formation of just my 3 primary roles for each character I hadn't created in advance. You just can't cover every possible formation, so you have to pick and choose. Considering that most characters are pretty bad at their off-classes, even if you develop them, it's hard to actually see much use in game for them. Don't get me wrong, they exist (I think triple Sentinel was hyped vs. telegraphed super attacks), but even if you do bother to develop the off-classes, they probably won't see much in-game use.
There is one possible exception to this. Synergist Fang is the only character in the game (pre-aftergame Crystarium) to get Bravera, Faithra, Shellra, and Protectra. In other words, there is actually reason to level her off-role and it's not a strictly worse shadow of somebody else's version of that role. Plus, there's a uniqueness argument. I wouldn't be averse to letting Fang have this, although if I were being hyper-fair, if she wants the Synergist abilities, she'd have to buy them using the same base amount of Crystarium Points as everyone else. This would mean ignoring a few stat nodes in her primary roles to get the inefficient low-level Synergist boosts, and would be a stat penalty, basically.
Unfortunately, assuming that the characters have spent 0 CP on the secondary roles adjusts the stat spread from the Wiki topic a bit. The bonuses are pretty bad, but I suspect it makes each character accentuate their strengths and weaknesses a bit more - Hope isn't getting HP off Commando / Sentinel, Fang isn't getting Magic off Ravager / Synergist, etc.
* Bosses. Are all insanely ubergodlike and unrankable, even more so than FF12 bosses. FF13 turns go by *fast* so a 2 minute fight is really about 15 rounds, and most boss fights take longer than that - 5 minutes to 10 minutes is more common. Even throwing away healing turns and including all the buffs / debuffs, we're talking about 30-60 rounds of pure damage to kill your average boss, or 12x-24x PCHP. This means that outslugging an FF13 boss is generally "do you have infinite healing yes/no" even for the sucky ones with bad damage and no tricks. There's actually not that many plotty bosses anyway - not very many characters bother to chat and introduce themselves before trying to kill you. And surprisingly enough, despite it being one of the possible ways the game's plot could have unfolded, the party doesn't go on a tour of Cocoon's fal'Cie followed by killing them all in awesome boss battles. Not to mention that the fal'Cie are a pretty quiet bunch anyway, with one exception.
The one boss vaaaaaaaaageuly rankable:
Anima - Great scene before this guy at least. Has two extra parts, can regrow them, does damage. Chrono Trigger boss, basically. HP isn't as insane as later bosses, too. Fun fight that is quick and deadly! If it wasn't a fight that translates boringly to the DL, alas. The party is a bunch of mortals for this fight so not many tricks aside from "toss potions" on their side as well.