Planning on getting a bike (Cadillac L-3) that only comes with a Nexus Inter-3/roller brake. Would like to upgrade to a 7 or 8 speed internal hub. Haven't seen the bike yet to measure, but I fear that the frame might not be the requisite ?130mm? , and it's an aluminum frame, hence no cold setting. Assuming the frame is wide enough, is this possible? If not, what are my options? 7 sp derailleur?

Thanks,
Marty