It would be great to have a paperdoll for equipping champions. This has been the standard for years.
This could also be used to tweak itemization. Why can path of the mage characters equip a 2-handed axe? Why are assassins wearing plate?
I don't think anything's tied to the path or usage of a character currently since there aren't officially "classes" as in many other games. I agree there should be some restrictions. There are some currently, like how you can't use a 2-handed weapon and a shield, but I'd think they could add some others in, too.
I know the paperdoll has been brought up before. I think in WoM they added some arbitrary restrictions (only up to 5 rings, etc.), but I'm not sure they're present in FE yet.