What if in an RPG, there was a mechanic where you could treat any spell like Pokemon's "Future Sight" attack, where nothing happens this turn but you could then perform (basically) a second attack next turn. That way, you could deal extra damage to your foe at the cost of one turn (hell, to make it even better, you could give the attack a small 1.3x boost to offset the turn deficit). This could combo into some other moves, by hitting for weakness and immediately dealing powerful boosted damage all in the same turn.
Now, imagine the reverse. A Double-Cast that allows you to cast two spells in one turn, but you can't move the next turn. You deal a ton of extra damage, but if you don't deal significant damage this next turn, you're now a sitting duck waiting to get your ass handed to you. This creates yet another risk-vs-reward interaction where you must weigh your options before taking action.
Now imagine... if they stack.
Like, first turn you cast "Delay/Charge/Future Sight", and you set up an attack to go off next turn. Then (after an ally either heals you, protects you, or does something else to offset the damage you just took), you cast Double-Spell in order to get two attacks off this turn. Then, after those attacks deal their damage, the first one goes off with that extra 1.3x boost. This means that, at the cost of 1-2 turns of free damage, you deal over TRIPLE the damage you would have normally done.
This will have to be balance-tuned before someone applies it to a real game, but it would be so cool to see in action. Lots of risk-and-reward in play, and if a player has enough skill and tactics they can mitigate the risks of the combo while still taking advantage of the three-attacks-in-one-turn setup. I REALLY like the potential this idea has.