Some ideas I think would be cool additions to the game :D
Placeable Spawners that spawn certain amounts of troops over intervals of time, but cannot exceed a maximum count of active units already spawned by it. The troops that spawn, the amount of time needed to spawn them, and the maximum amount of active units from each Spawner can be customized by the Player in custom battles. This could result in longer battles and can be used for creating separate waves of attacking units, reinforcements for when battles get difficult, a constant force of attackers and other miscellaneous purposes that the Player can create.
More Randomness in the Random Battle gamemode. At the moment it always follows the same algorithm when generating a random battle(outnumber the player and its forces). Also, the objective of EVERY random battle is to reach the end point. perhaps an intense King VS King battle or a Deathmatch massacre randomly decided by the game?
Custom Units for Custom Battle. Perhaps the player wants to lead an army of pitchfork-wielding Vikings with ight armor, or a squad of unarmored fire swordsmen? The Player would be able to create and save their own combinations of equipment for NPC units, which would inspire further creativity in battle!