So you will be running it via a capture card or something?

Anyway some dashboards will have some flavour of SSH or telnet which could probably get something done there, and I dare say you could probably do something special with python on XBMC.
Kill signals... that one is harder as the amount of stuff running in the background is a bit more limited and the original xbox lacks the nice middle button of later xbox lines. Though if you wanted I guess you could rig something up to the power button -- it would be a simple trick with an arduino or something if one of the old power button and such mod chips (assuming you want to/can find one and deal with the aggravation of using them) does not have such a feature.

So yeah some kind of possible I guess, however I am not aware of any "oh it is just an option of xbmc/evox/unleashx/this mod chip/this custom bios" short of something you might be able to get XBMC python to do, XBMC has some pretty decent network control capabilities (including up, down, left, right and go if nothing else) you might also be able to latch onto. You might also be able to chain load something that in turn reads a text file which then launches a further game according to its contents if you are especially tied to FTP.

Frankly it seems like a lot of effort to go if you are within video capture distance of the device. For my taste it is a lot of effort and I would probably only do it as part of a hotel or an arcade type setup for somewhere.