Actually, I might go with either Rider or Caster for James. He fills out a niche for either team-up, the ability to throw up an information infrastructure with one, and decent anti-Master combat ability even without any potential buffs for the other. Plus, the interactions could be decently interesting. For example, looking at Caster's bio in the dA page, there could be some parallels drawn between James and Faust's upbringings.

Also, I'd be willing to have Archer look for a new Master and give Hakuno to someone else, if the player in question wants and Roxas is down with it.