I could test it, but I don't have freaking idea how to even start trying USB hostmode under Debian. AFAIK, it require "hostmode patches", which are (very) hacky implementation of USB host, included in kernel-power. Were they even upstreamed (I doubt)? do we have possibility to use them under native Debian (doubt +1), somehow?

/Estel

// Edit

Going back to OP use case - if hostmode is not possible, the way to go is to use USB networking (aka, be connected with other device that have LAN port via USB, and use network over it), which definitely works, without any problems. If your router doesn't have USB port/can't be hacked to have one (like, for example, good old Linksys wrt54G*), the 2nd devicemay be something cheap, like Rpi (although, I would kinda wonder why you're not using Rpi for the server, then).