Do I really still need both lenses here? Maybe I need to replace the 35/1.4 Lux with a wider lens? I don't have any wider lenses that are excellent and that work well on the M9, though. Maybe the Rokkor 28/2.8M or the Kobalux 28/3.5?
Do you need both 35 and 45? No, but I think you should keep both.
If I were to get rid of one, I dont think I could help choose. Both are worth having, the 35 as a "bring only one" lens and the 45 as an indispensable part of a duo when paired with a wide lens. Plus you're a 50 guy and that 45 contax planar is one of the best "50's" ever made.
You could never "replace" that 35 of yours with any lens really. Maybe you could get close, suppliment it, or mimic it with another 35, but that one is so unique and also a piece of history.
However, I would say that I think it would be worthwhile of you to at least consider adding a wide angle lens to go with the 45/50 when you want something wider than 35. 28 is the logical choice. With the new releases of the 28 elmarit and summicron, prices on those have started to drop. I would consider those first. Or you could seek out a Contax 28mm and get it converted. Would be a fun combo on an M9.
As a semi-wildcard, you could also look for a 21 instead of a 28. While it is a big jump between 50 and 21, it isnt unreasonable if you really are a 50 shooter. It will require you get close to what youre shooting, but for travel and pictures of buildings, landscapes, museums, etc, that usually isnt a problem, and can be a big benefit. The closer you are to the point of interest, the fewer other tourists there are between you and it. Also a little easier to handhold at slower speeds and zone focus than 28.
Also, when paired with a 35 a 21 makes a great duo.
For me personally, 35 is a bit of an odd duck. Most of the time I find it too tight and too wide, especially when traveling in European cities. 28/50 is perfect for me in those locations. On my last Euro trip I brought 21/35/50 and found that most of my 21 shots needed a lot of cropping and the 35 didnt get as much use as I was expecting because it felt too tight when walking the streets.