Persona 5

[SnowFire]

I actually have tested Shock with Fast Heal as well (on Noir); it wears off instantly!  Okay, not quite true, it'll last until she takes a turn, so hypothetically enemies could inflict Shock then attack for Technical damage if they have a double turn or the like, but the point is, it denies 0 Noir actions.

I suspect the confusion might be for "# of turns denied" vs. "number of turns the effect is up if you want to exploit it for tech damage."  Shock denies a single enemy turn, but you can hit them for tech damage both before they got the denied turn and before they get their fresh turn, since the effect wears off the second they get the turn (to stop infinite status-locks).  So Shock is 1-2, Freeze is 2-3, etc. if people disagree on what duration is measuring.  e.g.:

PC1: Inflict shock
PC2: Attack (tech boost)
Enemy: Pass turn, shocked
PC1: Attack (tech boost)
PC2: Attack (tech boost)
Enemy: Shock wears off, enemy takes turn

Also, re your questions...  eh, they're mostly only relevant to Joker, who is already an interp and research headache.  Just for some semblance of sanity's sake, I'd probably ban everything (Isolation for SURE, there's no way you have enough time to do that on L75ish Personas, and I don't really respect keeping an L60 Persona around solely to abuse this), but you should do what OK wants, not what SF wants.  The problem is that a "single" customization that would be generally useful is reasonable to do in-game (add Nuclear Amp to a Persona with Nuclear damage, say), but adding in 6x customization requires blank cards & multiple Electric Chairs or multiple Gallows save/reload cycles, and you can only Gallows once late-game anyway.  Joker ends up crazy enough as is without being able to drop Attack/Speed/Defense Master + Null your best damage on any Persona he wants.

Flip side, the one thing I certainly WOULD allow which you seem nervous about is max'd Confidant Fusions.  Even a very casual playthrough will probably max at least 50-75% of the Confidants, and I max'd em all, and even if held to only maxing some, it'd be easy to maximize the relevant ones.  It hardly matters since almost all of them are ludicrously overlevel, but I don't see it as a big deal.

EDIT: Huh.  Just got into a battle, and Freeze wore off on one of my PCs (Morgana) after only 1 lost turn?  I might take that hype back, it might possibly be variable length, because I've definitely seen 2-turn freezes (and confirmed a 2-turn freeze afterward).  OTOH, I just re-tested Shock yet again, and it's still one lost turn.

Also!  Judge of the Dead with components hype.  Since I presume the one-itemization-per-day limit still stands on the final day, I'm kinda leery of assuming Dungeon 8 randoms are "free" itemizations.  You gotta itemize a little earlier.  Anyway, for the sake of SCIENCE, on Mementos final mission clear after finishing Palace 7 (aka still time for some itemizations), I just made a Judge of the Dead!  Joker's Level 64 (since the more overlevel, the more expensive).  It cost 754,140 yen.  And left me with fewer Personas.  And I happened to have caught like 3 Treasure Demons which makes this easier / cheaper, but aren't guaranteed.  And I was also using the Persona fusion calculator.  If you include the cost of re-summoning the original Personas that were consumed, add another ~150K yen or so for a cool 900K total.  And that still isn't re-summoning the Michael for Joker to use!  It's... a tad pricy.

[Nephrite]

I don't know if this matters, but it looks like if you fight the 6th Palace Boss by themselves, they will transform into their second form earlier? I honestly don't know how this works exactly, but it makes sense since you don't have your party to handle the "gimmick."

Link Here Obviously has a spoiler and so on and so forth.

I have no idea if this changes any of the boss scripting.

[SnowFire]

As a random comment since it was somewhat relevant in Futurama (although not THAT relevant, since wind-elemental ID is something that Queen has trouble with anyway)...  I'd argue that the "storebought" status immunity gems are a bit shaky on legality.  #1, they're 80,000 yen, which is very expensive.  #2, you can only get one Gem of each type - you buy it, then they're sold out.  Now, you'll get a single strictly better all-ailment immunity accessory, so you effectively have 2 blockers, but that still doesn't quite make it to 4 as far as being able to outfit an entire party with a blocker.  Additionally, even if you did allow this, it's competing with various other single-purchase-then-sold-out accessories which are extremely good, packing the likes of Auto-Tarukaja.  So if you subscribe to Elf-esque penalties for equipping a stat-blocking accessory, it's a substantial hit to equip it.

The good news is that that itemization accessories are a lot cheaper.  Anyway, from OK's lists, status that are stopped by itemizing monsters:

* Itemize: Fear, Despair, Shock, Rage, Bless-elemental Instant Death, Burn

Status blocked by Gem purchase not blocked by itemize purchase:

* Gems: Hunger, Sleep, Freeze

Status you are out of luck:
* Brainwash (unless you allow paid DLC single items), Confuse, Dizzy, Forget