Ok...my opinion is, if Channellers are the only ones who can tap into magical forces, why bother giving spell-related perks to Champions who are unrecruited at all? I like the Imbue system myself, but they shouldn't have like, Fire Disciple before someone hires them, Imbues them and then they gain a level and select that perk. Or if you're going to give one of those perks to a Champion, make it so they're carrying a tiny shard of one of the big elemental crystals that is the source of their perk. One you could take away if you felt like it.
Like I said, I like the Imbue system, but giving Champions affinity for magic before they are Imbued is basically countering your fiction about Channellers being the only ones who can use it.