4x100 rims ?

Um. No.
Unless you have a Gen 1, Gen 1 or 2 Miata, and various other Mazdas, Toyotas, Hondas, etc.
The 08-13 (on?) xB uses 5x114.3 (5 lugs on a 4.5"/114.3mm circle)

would it be possible to change the hub...

Possible, yes, but very involved, as it involves changing the brakes, too, and finding a source-vehicle that had a hub that will mount onto the xB's mounting points (MAYBE a 4-lug, disk-break Corolla may work, but never tested it).