If you're truly more interested in the business side, why don't you build it as quickly as possible in rails/django and then later if it warrants it you can hire some people to build it in lift/something else?
It sounds like you are spending time/effort worrying about scaling way before needed. If you can solve your problems you have today faster then I would do that, not hinder yourself today for possible problems way down the track.
A certain language might be twice as fast to get work done in, but you can be 10 times as fast if you are enjoying yourself and motivated.
I just wouldn't kid yourself that scaling is the reason for the choice. Just enjoying it is plenty of reason.