Making troops and ships tradable, especially ships is not a bad idea. I know I have wished I could do that on more than one occasion.

in this engine so far the player has been limited to only 20 units.

The older engines had reinforcements controlled by the AI but not this one.

I Kingdoms you could switch between units and give orders but for what ever reason this one does not even allow AI controlled reinforcements other than the rare occurrence of an Ally aiding in the battle.

They have always demurred at making larger troop concentrations. I don’t see them raising that in the near future.