I have tried the WATE Leica lens and though it is convinient (in a way), I did not find the performance particularly spectacular. The 16 mm setting is similar to my 15f4.5, the 18mm is not as good as the 18f4 Distagon and at 21mm it was on par with a 21/4 VC. Bear in mind, this was not a scientific test, it was shooting as I usually does. What turns me off the WATE is also the price and the finder! For that kind of money I can buy a 15f4.5 VC, a 21/4,5 Biogon (considerably better than the WATE) and a 18f4 Distagon as well as the finders for these lenses and I still would have enough money left over to get an extra body or two (a used M6 and a Bessa R4M) and some more film!
The 21/2,8 Elmarit was an OK lens, not as good as the Asph version, but i would do fine for most stuff. I did have a couple of them, but switched to the ASph when it came out, disposed of the Elmarit 21's and kept my Super Angulon as I liked the "signature" on that lens better.
I kept the 21 Asph for many years, but I never really warmed to it. It is a big "lump" of a lens and though very sharp and contrasty I switched to the more "petit" 21f4 VC when it came out. If I need the extra stop today, I use my 21/2,8 ZM and so far, I have not seen enough (if any) difference between the performance of the 21/2.8 Asph and the 21/2,8 ZM to regret getting rid of the 21 Asph.