Very nice the idea of rotating nut!
I want to convert a conventional lathe to cnc and Z axis leadscrew has 1900mm length 30mm diameter.
If i use L1900mm 3210 rotating ballscrew with 2 bk25 end supports i will have 1300rpm citical speed & column strength 28477 newton
The critical speed is ok to me because i will get 10m/min rapids with 1000rpm in ballscrew i have concern about column strength because 28477 newton (2900kg / Z axis servo can give 3400kg ) isn't to big force and also i have fear about sag to 3210 ballscrew and runout at rotation that will do a lot of vibration.

In my situation would be better a rotating nut design like this to overcome these 2 problems (column strength & ballscrew sag/buckling) ?
Also with rotating nut design can i use a lower diameter ballscrew without having whipping ?