That is an excellent question, and one I have pondered myself. I think the issue in our climate ( I am not too far from you ), as you mentioned, is cycle time and heat. There are short cycle bananas that do flower and fruit within a relatively short time period, but I think they are fairly finicky when it comes to cool weather.
I think fruiting bananas outside of the tropics or sub-tropics is, and will likely continue to be, a very hit and miss affair which will require a lot of luck, and extensive inputs by the grower...either time or money or both. It certainly can be done and many people have, but I gather it is not an easy process.
I would be interested in M. basjoo crosses if that is even possible. It seems to me that would be the most promising companion for a northern edible banana cross. Maybe a basjoo and a short cycle
- I really may just be dreaming...it would be difficult enough the get the pollen and flowers together...although maybe pollen is shipable?
There is a cross supposedly between M. sikkimensis, a cold hardy banans, and M. chinichampa, an edible one, called Helen's Hybrid. In my experience (seedlings) it most definitely seems hardier than Dwarf Orinoco but won't overwinter outside here. I haven't fruited it, and don't know if I will ever be lucky enough to do so, but it does grow well here through the growing season and might be a viable option for fruiting. It is supposed to have a decent fruit with seeds. I posted a little bit about my experience with it here
Musa HH, my experience
Anyway, It certainly could be fun to play with....so I too and interested in any educated responses