Hmmmm....
I don't know if the Axiom rack will work with the Alfine's axle. I didn't think about that part.
I also don't know of any other rack-bag system that's as handy as Topeak's. I haven't used the trunk bag much since I got panniers, but I've also used Topeak's basket, and I also like how easily I can swap them to the beam rack on my FS MTB rig.
So... ergh... you may be stuck with P-clips. Unless you can swap the Kona for something else..