You might start with your 'lots of gears' criterion. A Pinion gearbox will give you a wide range and 18, unduplicated speeds. I believe there are numerous bits with 26" wheels built around such a gearbox. I have a Tout Terrain that has flat bars, Pinion gearbox, built in rear rack. It is a little heavy, but it has a sturdiness that is comforting off the pavement.
Good luck