The character concept clearly indicates, that the character does not create the items himself, so any focus item would in no way affect his enchanted items. Without a casting power, focus items are extremely useless, so the only thing that remains are enchanted items. Usually a non-caster can't even take refinement, but in a case of a character concept like this, I as a GM am willing to make an exception (or a new power if you will) to accommodate the player's idea.
It is by its very origin a matter of agreement between the player and the GM, which includes any matter of game-breaking you might worry about. Yes, I'm invoking "the GM decides" again, for one, because I don't think it is a bad thing, and two, because a character that uses magical items like this is not covered under the RAW, so you'll have to make it up as you go anyway.