What to do with Winter Robin

I pulled an off IV Winter Robin on the legendary banner and already gave a fully merged Effie and a 4* merge Gwendolyn, so his destiny is to become fodder.

Both Brazen Atk/Def and armor March are obviously useful; and it seems like Tannenboom is a pretty good enemy phase weapon).

Does anybody have any suggestions on his best role as fodder?

PS - relevant info - my only current armor March unit is Amelia, who is the primary green on my armor core.