BASHMAN
Basic Action Games
In another thread, I proposed this idea: each spell has an At-Will, Encounter, and Daily version (or at least some spells do).
The Daily version can be used once (well you can choose to prep 2 Daily Sleeps, but you get what I mean). Encounter can be used each encounter, and at will is at will.
Maybe some spells only have 2 version, but oh well.
So Magic Missile: At Will: 1 missile does damage = to INT mod.
Encounter: 1 Missile per 4 Levels.
Daily: 1 Missile per 4 Levels, each does 1d6+INT Mod.
Sleep:
At Will: Targets are drowsy, gets Disadvantage and half-movement until attacked or shaken awake.
Daily: Keep it the way it is now.
If you want to add some more "flavor" to this, you could also make the different options "unlockable" at certain levels. So a Wizard would not get the Daily Magic Missile at level 1, but might gain that at level 5. So some spells get better as time goes on. Note that the at-will version never would change.
As an option, you could make it so that once the Daily of a spell has been cast, you lose the Encounter and At-Will versions of that spell for the day as well. However I could see this being a problem.
The benefit of having each spell have a Daily/Encounter/At-Will variant is that it makes it so you don't really have to have different kinds of spell "slots". If you can cast 2 level 1 and 1 level 2 spell per day, and you pick Sleep, Magic Missile, and Phantasmal Force (I hope that comes back as a level 2 spell), you've got 3 At-Will, 3 Encounter, and 3 Daily spells figured out.
The Daily version can be used once (well you can choose to prep 2 Daily Sleeps, but you get what I mean). Encounter can be used each encounter, and at will is at will.
Maybe some spells only have 2 version, but oh well.
So Magic Missile: At Will: 1 missile does damage = to INT mod.
Encounter: 1 Missile per 4 Levels.
Daily: 1 Missile per 4 Levels, each does 1d6+INT Mod.
Sleep:
At Will: Targets are drowsy, gets Disadvantage and half-movement until attacked or shaken awake.
Daily: Keep it the way it is now.
If you want to add some more "flavor" to this, you could also make the different options "unlockable" at certain levels. So a Wizard would not get the Daily Magic Missile at level 1, but might gain that at level 5. So some spells get better as time goes on. Note that the at-will version never would change.
As an option, you could make it so that once the Daily of a spell has been cast, you lose the Encounter and At-Will versions of that spell for the day as well. However I could see this being a problem.
The benefit of having each spell have a Daily/Encounter/At-Will variant is that it makes it so you don't really have to have different kinds of spell "slots". If you can cast 2 level 1 and 1 level 2 spell per day, and you pick Sleep, Magic Missile, and Phantasmal Force (I hope that comes back as a level 2 spell), you've got 3 At-Will, 3 Encounter, and 3 Daily spells figured out.