there are now quite a lot of frames out there with vertical drops and an eccentric bottom bracket (EBB) for chain tension for SS or IGH use. the problem you're going to run into, as has been mentioned by other posters, is that just about all IGHs require nutted axles as opposed to a quick release lever.

i have a Scott SUB 10 that has an alfine 8 IGH with vertical drops and an EBB for chain tension. while i don't have a quick release axle for my alfine, the vertical drops are still nice because it allows the bike to have disc brakes (i freaking LOVE disc brakes), something that becomes a lot trickier (or even impossible) with horizontal drops.