Interesting idea Sean, but I don’t think it’s doable in Xlobby alone. Filters in XL would narrow down search results, but you would need to have search results to begin with, which is not what you going for here, I think.
On the other hand it should be doable in plug-in itself, I would need to intercept keyboard strokes and perform a search on any alpha or numeric ones. Let me see what I can do here, I’ll try to get back with you around weekend.
EDIT: Or, it may also be doable with girder – same idea as above.