I just came to search for this same answer, for basically the same reason. I'm updating my unRAID server, which now allows Virtual Machines to run under XEN, which can/will allow for PCI passthru of hardware to a VM.
My Plan is to install Windows in a VM, and run MC in that VM, with the TV card and GPU passed thru to Windows (and therefore to MC), but with direct hardware access to the storage/drives, to allow me to replace my physical HTPC.
My hope is to soon be able to run MC as a server in Linux, just to serve media to all my devices. I want to use my phone/laptop/whatever to select media to display on the monitor connected to the unRAID server, or device via Gizmo or webmedia or whatever.
It sounds like this is not currently possible, but hopefully it can/will be possible soon.
I wonder, would it make this easier/possible if MC was 'restructured' to just 'serve' the media with the server portion of MC, and let all 'playback' duties be handled by the connected client/machine/device? Meaning, don't try to process/decode/whatever the actual media files with a server install, just send the bits to the client untouched, to let the client/device handle any conversion/decoding stuff.
Anyway, fingers crossed for this to improve soon