I would like consistency with the immune to magic trait, too. I have had instances where I can't cast a strategic spell (tremor, freeze) on an AI stack due to the Ophidian immunity, yet my pet Ophidian does not confer the same benefit.
That could be a great strategic part of the game, and make those few magic-immune units very valuable.
Stuff to add in FE:LH 2.0 I guess!!