Buying a new bike with drop bars, with the intent of immediately switching to upright bars, doesn't make much sense. You need new bars, brake levers, shifters, stem, grips, maybe cable housing. Why not buy the correct bike to begin with?

Considering a single speed, that you're going to load with porteur rack and presumably loads, when all the other bikes you're considering are IGH, doesn't make sense. Converting that single speed to a Nexus 7 IGH will be costly and, again, why not buy the correct bike to start with?

I think you should make a list of the attributes you want in your next bike, and then look only at bikes that actually fit that list. Your thought process currently seems a bit scattered and random.

Also, if you are able to work on bikes, since you're talking about swapping bars and converting a single speed to IGH, why not use the Superbe? So it needs new wheels including a new hub, what's the big deal. There is probably a Sturmey Archer hub that is a direct replacement for the original.