I would get the SL2 and use with M-glass or Panasonic L-mount glass. The Leica glass is way too heavy and expensive for my tastes. The Panasonic L-mount looks great but I haven't used it myself.
I just got a Sigma fp and am using it with the Sigma 45mm f2.8 and adapted Sigma SA lenses. I am very happy with the images and appreciate the small size of the Sigma fp.
But either way, SL or SL2, you can't go wrong.
Eric Triplett in sunny Florida
These days I shoot mostly with Sony A7Riii, Sigma Quattro SD H, Panasonic G9, Panasonic GH-5.