Changing nozzle on U1 takes about 10 minutes for each tool head, so it’s a 40 minute process every time you switch nozzle size.
I hope you are working on a more efficient way to change nozzles. Meanwhile, please sell 0.2, 0.6 and 0.8 nozzle with toolhead. That would cut down 2/3 of the time.
I’ll probably buy some additional print heads as well so I can equip them with different nozzle sizes. Swapping print heads is significantly faster than swapping nozzles.
But the print heads are still very expensive 
It’s an expensive solution. I hope U1 can use mix nozzle size in the near future.
U1 is $769 for existing owners during the 10th anniversary sale now, very tempting but I can’t find a space for it.
I have limited need for different nozzle size(s) but I’m thinking about getting a spare Toolhead 1 (left) and a 0.2 nozzle and only swap that first toolhead for those special prints. Since I will only print 1 color item(s) I figure I change the nozzle size in the software to print 0.2 stuff, and since I won’t even be using the other tool heads I spend less than $100 for those projects and still have my main 0.4 toolhead available for easy swaps when I want to do multi-color stuff. Just can’t justify $330+ for a full set of toolheads and 0.2 nozzle set…might as well buy a 2nd machine and swap all of those nozzles for full set of quick change options, imho. This plan also gives me yet another spare 0.4 nozzle and the “special” left toolhead in case the original has an issue. Any thoughts on the logic? Regards.
See here: Prusa Slicer