Another freewheel option if you need serious tooth count is a custom Circle A.
Europa, I am considering the exact same idea as you but like the look of the sturmey 2 speed kickback. The only thing holding me back is i would have to uprgrade my wheels to 36 H spoke and dont really want to spend the dosh. I also like the look of the SRAM Automatix 2 speed but this Hub shifts gear automatically and I dont want a machine dictating to me when I need to shift. I will probably change from 48t down to 44 and see how that goes.