Well first I don't use or like EVF. There is nothing better for the street than a rangefinder. I prefer it. The original MM doesn't have all the stuff I don't want on my camera like live view, EVF, a crap load of FPS, (I don't need or use any), auto everything, and the MM is a pure B&W rangefinder shooting experience which is quite a difference from all the other choices out there. Nice to have choices.
As far as sensor to get one modified/converted don't they burn off the CFA filter which can leave some color pixels, anyway wouldn't a camera manufactured to be B&W be a much better choice?
I had a darkroom until a few years back and divorce, downsizing and client base forced me digital. I studied the zone system in college in the 1980s. Yeah I did all the tests. The school had a densitometer. Drew up all the film curves. Also along with shooting professionally full time since 1986 I also did custom color and B&W printing. If I still had a darkroom I would probably still be shooting film in some capacity. I don't but I can tell you this; the MM is the first B&W digital that I have really liked. My old college professors and I are amazed at the ink jet print quality that can be gotten from the MM files. The MM is the first camera that has given me the same feeling I got when I bought my 500 C/Ms in the mid 80s. Someday I might just go back to film. Maybe buy and old 8X10 Deardorff move out west and shoot large format landscapes but for now the street is my passion as I thought landscape was when I was studying large format zone system photography in college. I worked on a documentary project when I was in school and I found a passion for the streets then that I never found with landscape. And I had yet to enjoy working on the streets as much as I have since picking up the MM.
The reason I wrote all of this is I know what good B&W output is. The MM is as good as digital gets period. I have shot with almost all of the high end Canon and the files from the original MM are so much better. I can only imagine how good the files are from the new MM. My files even at ISOs of 1600 and deliver prints that I would compare tri-x negs shot with my 500 C/Ms processed in Rodinal 1:50.
I am perfectly happy with the original version and I have no plans of upgrading to the new camera. It has more stuff on it than I want or need. My current version is terrific at 1600 and 3200 ISO.