pass-through comment is a good point, I don't have a clue on the matter.
I'm certainly not asking you to build a driver just for me. By reading here and there, other people are using firewire card and might have run into the same trouble.
I am considering building it myself (not so sure about my personnal capacity to do it) but I would like to read others' comments whether it is possible or not before going further. Expenology is build on linux, VMM is not even the good option. Once driver is "build" (no the easiest part I agree) it should run smoothly, right ?
One may ask why bother with this, the pb is that the only capable (strong, efficient) machine with ieee1394 is presently my xpeno nas ...