Except for the fact that in a per day system your are supposed to sleep to regain your spells. It's not just a mater of time. This way developers can control the ability spam through rest areas placement, and at the same time they are free of consideration about timing.
Which is something that you can do with the click of a button to your homestead? I don't see the meaningful difference. Neverwinter Nights 2 supposedly had a system like that, but in practice, you could just rest after every encounter.
Neverwinter Nighs 2 (and pretty much all the recent D&D powered CRPGs) does not have rest areas. You can sleep wherever and whenever you want in that game. I'm talking about a game where you are supposed to find an appropriate place to rest. Again, this is not my favorite solution to the ability spam problem, but it's surely more functional than a long cooldown.
Rare reagents just means difficult to find, not limited to a 2 digits number. We are talking of a renewable resource. Just rare, or expansive, or both, not a finite one.
And why more, excuse me? In Ultima, for instance, potions and spells use the same base ingredients. Leaving alone the fact that "you don't want to add more stuff in the game" isn't really an argument here, considering that putting an arbitrary limit to the amount of stuff one carries around in this kind of games is - in short - contrary to their spirit.
I'm not a fan of reagents because it adds annoying complication for no real benefit. Instead of having to worry about one item, your mana potion supply, you have to worry about your supply of 10-20 or more different components, each of which is used for multiple spells in different combinations and amounts.
A scroll-based rare-spell system would have you carrying around more than one thing, yes, but a scroll is only used for one spell, and using it won't affect your ability to use other spells.
I'm not against your scroll-based rare-spell idea. Point is, reagent DO have benefits:
1) Unlike mana they aren't a universal resource; so using reagents developers can prevent high level spell spamming.
2) They fit the "use/interact/collect as much as you can" philosophy of this kind of games.
3) They add "color" to the magic system. Spells aren't just other kind of active ability with reagents. They are something different.
That being said, it seems that we will have different casting times for different spells in the new building. Which is good, an it's also a new starting point to discuss further additions (if needed).
