- Increase the delay between rests for wizards.
- Increase the number of prohibited schools to 2 or 3 for specialists.
- Introduce spell components (on that one we're rather cold).
- Reduce the amount of bonus feats for wizards.
- Limit the amount of spells wizards can learn.
- Do nothing, it's fine as is.
- Removing scrolls from shops.
Of all these potential changes, the only one that makes any practical sense to me is to reduce the quantity of scrolls in shops, and would likely be the simplest tweak to implement. The ability to assemble the entire repertoire of wizard spells with nothing more than enough gold (at least up to 5th level spells) without ever leaving Barovia is ridiculous, and makes scrolls in loot almost pointless until you start finding higher level ones. Keep a core of essential scrolls in NPC inventories, and the UMD folks will have 80-90% of their needs met, while slowing down spell acquisition and making loot drops more desirable. You just need to make sure that all available scrolls are in the loot tables, so that wizards have a decent shot at acquiring spells.
All the other tweaks seem to be counterproductive. Resting should be mechanically the same for everyone (if a fighter with a high heal skill, heal kits, a bedroll and food can practically regenerate in a 2 hour rest cycle, I don't know why a wizard can't renew their spells).
Adding more restricted spell schools might be more PnP, but unless you have the ability to hand pick those, I think this might be too unfair, and you might end up with fewer and fewer specialist wizards (bad for player options and RP).
Spell components and spell books are great in theory and awful in practice, as they would appear to be a logistical nightmare (this is where PnP and computer gaming diverge significantly).
Limiting wizard bonus feats is not necessary in my view (I think the sorcerer feats suffer from being last in the pack, not wizards from being second to last in the pack).
Capping the spells that a wizard could learn is a throwback to old, old, old school AD&D, and might be kind of neat, but you would still have to set the cap relatively high to avoid crippling the class -- it would essentially force all wizards to become specialists, since they can't assemble the full spellbook anyway. They would use their allotment for a core of essential spells, and use the rest for a particular brand of flavor. Again, kind of neat from an RP standpoint, but I am not sure that the juice is worth the squeeze on that one, as you already have a lot of specialist caster classes available. There is a value to having generalists, and you want to retain the possibility of a wizard
finally getting all the spells for their spellbook (it would be a spur to get that last coveted scroll).
I have noted before that while the desire to mimic the PnP experience as faithfully as possible is laudable, there are practical challenges when a game is converted to computers, and even more so when adapted to real-time online play. The NWN version of D&D is significantly different (i.e. more limited) from the PnP in some critical mechanical ways, and adaptations are always going to be imperfect, so I am not sure that a unyielding devotion to the 3.5 PnP ruleset is always the wise or practical choice.