That is looking great. Nice size lathe. Are you going to use Vbelt drive, timing belt or gears?
For Vbelt or gears, you won't have to consider how difficult it would be to change the belt. Timing belt, however might require more work. I haven't yet wore out a timing belt though, but I am sure it can happen. Likely worth the trade off anyway with the compactness of your design.
I would suggest a few more ribs either bolted or welded. What type ways are you considering?
I look forward to seeing how this turns out. Welcome to the Zone, BTW.