Jim you're setting yourself up for a lot of work! I totally understand that real track has only 2 rails. If you want that look, I would start with Ross or Atlas hi-rail track and remove the center rail. Hand-laying track is tedious, and going down to Code 148 may get you into trouble with the flanges on 3R equipment. Most of the loco wheels are pressed on, so it's not like you will easily be able to swap wheelsets. Heck, you'll have to pull and press wheels just to turn down the flanges! For most of us, 3-rail O is what it is. Only a highly skilled few can make it into something it wasn't from the factory.
I like your idea of wireless control direct to the loco. Given the availability issues with Legacy hardware and signal issues with DCS, it makes sense. However- if you don't want to mess with batteries, you could get many benefits of direct RC by installing a "helper circuit" to rectify and smooth AC track power to filtered DC. The wireless receiver won't know or care whether the DC voltage comes from a battery or a rectifier circuit, as long as it's smooth and well-regulated.
If I decide to abandon Legacy and cash out (I probably won't because I have several), that's the way I would go. My $.02.
