Iâ€™ve had my 35 Summicron (goggles version) for nearly twenty years, mainly for use with my M3. But is does also find its way on to the M5 and M7 (0.72) from time to time.
I believe that particular lens design was produced in a number of versions SM, bayonet, and with special VF attachment for the M3. Optically, they are quite good lenses.
Some people hate the look you get via the additional optics of the M3 version, but it has never really bothered me, and I quite like the different view. The goggles also give the camera some additional character IMO.
I have taken that 35 â€˜cron literally everywhere and never had any problem with the lens, concerning the auxiliary viewfinder attachment. It has even survived many years of rigorous professional work, and it is still perfectly aligned.
My inclination would be to try and keep it in original condition, but others may have different views.