I would say go for the Skopar 35/2.5, the Cron 40 or Nokton 40 are also fine choices but for me personally they would be too close in FL to the 50s you already have. 40 would be a good FL, though for times when you want to carry only one lens and nothing else and of course it has the proper frame lines in the CL. BTW, can you see "around" the 40mm frame lines in the finder of the CL for using the 35?
The Skopar has very good optics, it compares much better to the competition than the Skopar 50 IMO. So if you are happy with the 50 flavor you will not be disappointed by the 35! If you are lucky, you could snatch up the C-Biogon 35/2.8 for around 500, which is again a step above the Skopar 35, a very very sharp lens and also less distortion than the Skopar, I think. The 1/3 slower max aperture will not matter, the Skopar is in reality more like a f2.8 lens anyhow.
There is also the Nokton 35 for around 500, I am not sure if it can be focused reliably on the CL wide open and in close, (same goes for the the Notkon 40 wide open), and it is bulkier and has weaker optics than the Skopar 35, so it wouldn't make much sense to buy one if you cannot make use of the bigger aperture.
I have personally witnessed some sample variation in quality of the CV lenses. I think it is simply a consequence of the lower price compared to Zeiss or Leica glass. Nothing to freak out about, just make sure you reserve a return right when you buy the lens and check it carefully and you should be fine. A different issue is the question of long term serviceability of these lenses. In Europe it is very difficult to get a CV lens repaired or serviced except maybe for very simple things like a helicoid regrease. This will only get worse in the future and this why I would not spend money on the more expensive (500$ plus) CV lenses. But I wouldn't hesitate to spend 300$ or so on any of the cheaper ones for that reason. I currently use a Skopar 21/4 and a Skopar 25/4. Previously owned a 50/2.5, 35/2.5 PII, 50/1.5 (M39) and 40/1.4