[JimMorrison]

I don't think there's a mechanism for having someone only affect the units directly under their command.

Pretty sure you would be limited to either an AoE Aura like Standard/Fear, or a Battlefield-wide effect.

If that were added to modding commands, it could really be amazingly cool. I would give a lot of the blander heroes thematic STR or DEF boosts, or whatever is applicable. Nothing huge, mind you, but it would be interesting if for instance, Auluudh from R'lyeh gave +1 MR to his entire army, because the presence of his mind is so powerful, it can shield all of those lesser minds, to an extent.

I know that if it's Battlefield-wide, technically this can be done with modding #onebattlespells on them, but none of the relevant spells are weak enough. I don't want Auluudh to give free Antimagic in combat, that's way too powerful. But if he gives +1 MR, and especially if it is allowed to stack with Antimagic, then it increases his utility in a way that could be seen as balanced, once other traits are assigned to other heroes.

Some other interesting ideas would be a totally Blind hero for Agartha, that boosts ATK and PRE in troops in his army, but of course only one army. Menopathos the White Minotaur could perhaps give 3% regen on the field. "Raterik" the Hero, et al, could give +2AP.

I could do this all day. :P