Stored and Conditional Casting
Two ideas that are related to each other. Usual disclaimers, sorry if already in or talked about.
First, stored casting. The ability to cast a spell, and then hang on to it for later use. I was thinking that perhaps the channelers could create physical manifestations of the spell for a slightly higher cost, so that they can cast a spell, and then use it at a later point. Or they could give the item to a hero who could then use the spell. Kind of like magic wands that the channeler can create.
EX> The channeler has some spare mana and doesn't need to cast anything, so he takes his spare power that turn and makes a stored fireball. If, later on, he is in a serious fight and has used up all his power, he could pull out the stored fireball and cast it using the item.
It would also be nice if these items could be traded off to other sovs. I might want to trade a sov for something and he wants the spell, but i very much do not want to give him the spell to cast whenever, so i give him a couple precasts of the spell.
Basically a magic wand idea, but for both minor spells for heroes, and major channeler spells.
Second idea is conditional casting. Similar to contingency spells from DnD, it should be possible for the channeler to cast a spell that has a preset trigger.
EX> he casts a summon fire elemental spell on a tile that is set to trigger if any enemy forces pass within 3 tiles of the spell.
Or, another example, the sov could cast a major dispel and set it to trigger if another sov casts a hostile spell on any of your cities.
Both stored and conditional spells allow for a lot more flexibility and tactics in spell casting as they let you prepare for the future and allow you to throw some surprises at other sovs.