If he has enough Res I wonder if Quick Riposte would be good for him. Would also help Aether trigger faster if that is a skill people keep.
this is what I was thinking as well. On Lucina I'd never use Aether, but with Quick Riposte, Heavy Blade and a tankier character it could work. Especially if the heal gets him back above QR range. It'd be nice if he can avoid being doubled by everything, but I don't think he needs to be a speed demon. Heavy Blade means no Fury which means he's not gonna be doubling the shit I see in arena anyways.
If I get him, knock on wood, his job will be green tomes almost exclusively. If his attack stat is high enough he won't need tomebreaker though. Fae and Tiki will become slightly bigger threats as he'd be replacing Lucina. I already have two very strong solutions for red swords and they aren't that common (nowadays).
Honestly I've already done most of this thinking for Xander, who I will go with if I find no other ranged counter red. If Ike's got stats like that but bent a little more towards Spd/Res than Def I'm happy.