re: SATA - does SATA definitely allow for this then?
Probably but not by design. The problem is getting the data accross many parralell wires to arrive down a long cable with out loss and in sync. This is easier if you have fewer wires.
but then to quote from the SATA web site:
What is the impact of Serial ATA on IEEE1394 (aka Firewire) and on USB2 in terms of PC system function?Serial ATA is planned to be the primary storage interface inside the PC system, and is not planned as an external interface to PC storage or peripherals. USB2 and IEEE1394 connections on the PC can be used where required as peripheral interfaces.
So your answer is "No" :-) But given I have seen it done with ATA66 I can't see why not.