Also came up with this concept for my game, I'd love some feedback on it.
Your character will have 7 attack slots available, using 1 slot each turn.
New attacks will drop from monsters and there will be a lot of different attack types.
You start out with just 1 attack slot and a standard attack that just does 1x weapon damage.
After a few zones you might find a new attack for example "Ice Lance, adds 100 ice damage to your next attack."
You can equip that now and from now on your attacks will have ice damage added.
Once you level up a bit, more attack slots will become available, up to a total of 7.
So, after going through some more zones, you unlock a second attack slot and find a new attack "Rock Smash, adds 100 earth damage to your next attack."
If we put this behind the Ice Lance, we create a synergy. The ice attack will freeze monsters and the earth attack will shatter the frozen monster, for bonus damage.
This creates endless possibilities for attacks and synergies.
Once you find an attack, you can equip it. Once equipped, the attack will level up as you kill monsters. For example after 100 monsters kills the attack levels up from level 1 to 2, with 10 or 15 being the maximum attack level.
Certain attacks at the maximum level will be able to be combined into new more powerful attacks.
In our example above, leveling both "Ice Lance" and "Rock Smash" to 15, would allow us to combine them and create a new attack "Snowquake" that deals both ice and earth damage.