I see no reason this couldnt be done with e.g. LTSP, at first glance. It doesnt matter what the network type is aslong as you can get drivers loaded for the NIC and a few megs per sec running thru it, and as far as I recall, g goes up to 45 or sumthing like that.. So, if you have a computer you can use as a terminal server, LTSP should be possible. Allthough, the solution you use is realy up to you..
Now, I have no idea if etherboot supports wireless cards, probably not, and that side might prove difficult all the more. So, that part will prove critical. Thus, the _easiest_ solution would be to have an external relay that would just cable it onwards to the HTPC itself.
But, a quick googling revelaed that this can be done, heres a quick link to get you started with ltsp wireless: http://sourceforge.net/project/showf...lease_id=79053
I wish you the best of luck with this, please do report back on you progress as ive been dreaming of this aswell for some time and may yet make my dream true some day.. (: