I'd like an M9 with a 0.58 finder.
Leica seems to have forgotten, with the advent of digital Leicas, that some of us wear glasses; some of us use 28mm and 35mm lenses; and some of us wear glasses and use wide angle lenses. Leica answered this need for film cameras by supplying .58 finders as an alternative to the standard .72. But for digital Leicas, as far as I know, the .68 finder is our only option.
Why were some of us forgotten? I think a .58 M9 would be as useful a tool as the other upgrades you get with an M240, M10, etc.
May the light be with you.