Mike,
I’d go for #26. There’s no compound curves. Make the railbus the next one. Rather than carve, I think I’d build a frame out of styrene strips, and then cover it with layers of thin styrene sheets.
Seriously, if you want some guidance, or assistance, I’d be more than happy to work with you. I’ve cleared up some space in my workshop recently, so there’d be plenty of room for it. I have some regular busy time already booked (Monday morning, Tuesday night, Wednesday night, and Thursday afternoon/night.), but the rest of my time if pretty flexible. Some mornings get booked that day because the weather is nice and we go birding. Hot days are always good for working in the basement.
I have an old transformer for my test track in the workroom - I’m assuming you want track power, though this could be a neat battery project. You might want something inside, just because you have all those windows.
1/29? Do you have any drawings or dimensions?