Hm. So you're suggesting that a USB host software module is written for the N900, then the data streams from that module are piped over the bluetooth to an external device that acts as the physical USB host for the peripherals causing them to be visible as standard USB devices to the system?

Never seen one of those or even heard of one, but the whole concept sounds simply pervy. Maybe doable, but the limited data rate of the BT link as well as possibly link latency (not sure how BT does on this front, as it's meant to be low power I'd guess it may suffer from slightly variable latency packet-per-packet) may well pop up as major issues. Maybe worth looking into, though I doubt the standard definitions of Bluetooth SIG may not include ready-defined profiles for such a thing. Making this work might be an excellent addition to someone's CV though