Sorry I didn’t read much I like you third bike. How much do you like it? If you love then buy a $237 Shimano Alfine8 hub with the $25 gear changer and another $25 to $40 for the shifters. Then you’ll pay $55 to $65 to get the hub installed into your rear wheel and have to pay ??? To hook up the gear changer and shifters if you don’t know how to. Or you could buy a road bike second hand for less and tighten everything up. Adding another bike to you collection. I’m at 13 bikes what are y’all at lol