Gotta ask, what is your reason for building this? is it mostly cost related, or do you want to enjoy the build of your own tool?
I was going back and forth a few years ago on building a spring pole lathe or a treadle powered lathe and finally had the realization that, that was a lot of work just for some chisel handles. I finally bought an old craftsman tube lathe from craigslist for $45 and made the handles i wanted. it takes up a lot less room and it turns out i'm not a big fan of turning so i'm out less than the cost of building it and i stashed it under my table if I ever need it again.
~Everyone has the strength, few possess the will~