In battles, use a Pokemon setup. Big party sprites in bottom left (turned back to camera), smaller monster sprites in the top right. Monster parties could go up to 6 members, e.g. two rows of three (think Suikoden). Back row is unassailable as long as on the spot in front of it (and maybe also diagonally related spots - maybe if they're occupied by relatively large monsters?) there's a monster. Of course, missile weapons and ranged spells circumvent that and can attack anybody. There may or may not be a damage penalty for that, I vote no.