Thanks fot the thoughts and replies.
Speaking about lens coverage, the 135 was initially sold to fit Retina IIIs and Retina reflexes, so in that case they had to cover a full 35mm frame, and they did, as long as I know. I tested the coverage using a spare Rollei ground glass and sharpness looks decent, things might get all swirly in the edges but in the end it's a fun project .

In my mind I was thinking about something more portable, not pocketable but almost, considering it's not a lens in shutter. That's why I mentioned Super ikontas and such vintage folders, but I live in Europe so I've never seen a Speed Graphic/Miniature/Pacemaker2x3 in the flesh so they might be smaller than what I think.