Yes, I have utilized that modification for the game with SCS1/2. It runs perfectly fine (atleast ran fine, on as much as I have played on BGT. Which is about one half of BG1 game)

But I didn't like it much and I am currently playing a mini_my_version_of_BiG BGT game without the modification.

Reason attributed too:

1. As your character levels up, you don't actually need the mod because you have quite a number of spell slots (directly due to character levels or indirectly).

2. Reduces gameplay interactions/features,
--like many spells redundant (as you'll never ever use them. As you get access to high level spells..you'd mostly use them and wait for the cooldown, rather than use low level spells)
--makes repeated, but fun part of identifying items redundant (as you can have one slot of identity spells and keep spamming it)
--spamming heals (making you not to utilize healing potions or other characters to have healing ability)
--having limited spell slots pushes one to think what would be the best combination of spells to have for either prepared or unprepared scenarios (else you'd just have one or two spells and keep spamming away the same thing every time)
--etc

3. Spell casters are already powerful in the first place after a few Character levels, with this modification you'd be outright breaking the game out of its socks, nickers and whatnot in BG2; when you have access to some mind blowing array of powerful spells and casting it over and over, again and again. <- can really turn out to be boring with the mod

4. You anyways need to rest
--To rejuvenate from fatigue..
--Trigger some In-Game events (Dream sequences in BG1 and BG2)

Thanks a lot for the detailed response. Actually a lot of the reasons you mention are my concern as well, especially regarding the game balance. If it is too easy, it really isn't worth it.
But I'll bring an example of why I think resting can be extremely immersion breaking. At the end of BG1 you go to the Sarevok ceremony well rested and prepared, as expected. Then all hell breaks loose and you start chasing your hulking half-brother for the final showdown. On the way there you get acquainted with several new friends, Undercity seems to be THE place to be at the time, including several packs of tough undead (either from SCS or BGSpawns, I'm not sure).
So you reach the temple's doors and your party is pretty drained by now (if you didn't play a war of attrition with weapons only and cheap tactics that I find utterly boring). Since entering unprepared and not on your peak, against enemies several levels higher than you, is very unhero-y thing to do, you decide.... to take a nap... for a good 8 hours... No rush, you know Sarevok will wait patiently inside, he's a good sport, right?

Of course liberal application of suspended disbelief will do, but if that mod, with the proper timings, can do it seamlessly, then even better. i will probably have to experiment with the timer.

Thanks for the heads up. :)

That is a good point, and it's possible to rest after every single fight if you want to, and then use the best spells to wipe out goblins or whatnot, then sleep again. However, I do prefer this system over mana and such, as that means you can more or less spam great spells non-stop, and never have to worry about running out. In normal fights in BG you have to be somewhat cautious, and it's often a case of "what will *just* kill these dudes so I can move on to the next fight?".

It also makes it more worthwhile to multi-class as a warrior/mage, and put on good equipment when you're fighting random grunts, then strip down to your underwear and start casting Timestop and Abi Dalzim's Horrid Wilting when it's time to fight at your true power level, as they say in shounen anime.

I don't know of any mod that does this. There's likely a console command that replicates the restoration effect from Wish, but I don't know it offhand. What you can do is this:

Download and install Shadow Keeper. Open a save game, scroll over to the memorization tab, and edit the max number of spells per day your casters can have. You can give your first level mage 80 spell slots if you wish. Go one or two tabs to the right and edit the number of memorized spells for your priest or mage.

Voila. Now you have a ton of spells that will reset on every rest, so you don't have to rest very often. If you wish to keep this max number of spells, you'll also need to go into your Override folder and edit the MxSpl___.2da for each caster class, so you keep these higher numbers at each levelup.

Thanks for all the responses everyone. I think I'll give iiSpellSystemAdjustmen a try first. I like the idea of having spells on a "cooldown" system rather than resting to restore them. It means I cannot use the spells so much that it breaks the game but on the other hand, I can go longer periods of time without resting and can actually use my wizards for magic rather than archery most of the time.

One last question though before I go ahead. I noticed it's in the "Baulder's Gate II" section but does it actually work for both games or just the second one? If it's only the second, if I use the other mod to thrust Baulder's gate into Baulder's Gate 2's engine, can I use the mod then?

I think it's only for BG2 engine, but you could use EasyTUTU or BGT to apply it on the first part of the trilogy as well.

Personally this is the only way I consider playing the Baldur's Gate saga anymore. The original BG has its charm of course (and a few things done better) but after getting used to certain improvements from BG2 it's hard to go back to it without missing those.