Stefan,
You will not be ill served by any of the cameras you’ve listed. For some folks there is something about the feel of a Leica. I’m one of them, love the feel of my old M4-P but it didn’t stop me from selling it and switching to a Nikon S3. Change, learning and growing is a part of life, the right camera today many not be what you end up with long term. Heck I have many shirts longer than some folks here have RF camera systems.
When I first came back to the RF world after years in SLR land I got a new Leica. At the time I saw some used Nikon SPs on the other side of the counter and now I kick myself for not having looked at them. If I had gone that way I would not have learned as much about lenses, cameras, photography or me. Getting a new M6 when it first came out helped me learn I did not need to have a built in meter, though I liked it.
I used to carry around WAY too big a SLR bag, multiple bodies, lenses, flash, just in case. While my S3 kit has grown the four lenses, most of my Leica and Bessa kits were three or four. I use to do three but found I preferred four and a LOT of space on the ends (15, 25, 40, 105). You can buy every focal length lens out there for most of the rangefinders but on the positive side most are much smaller, though can be a lot pricier.
Look at it as another step in your journey of learning and enjoying photography. Take a look at the CV glass in addition to ZI and Leica old and new. There is some world class glass that comes from other places (e.g. Nikon) that you might want to check into.
An additional approach for the 15 if you go ZI is pick up a ZISW as a rear lens cap and just leave it on. I did that with a Bessa L for my 25 for both my Bessa and Leica kits and it was very flexible. The key is light weight and small. The L was perfect for me, the SW might be for you.
B2 (;->