My apologies for the below; I think I see what you may be getting at. OP's frame has a shifter boss with lever stop and cable guide on the left side, just like that on the right. Down near the bottom bracket it has a cable housing stop on each side of down tube and another on the right (drive) side chain stay. On the right, one inserts a piece of housing with ferrules to facilitate the angle transition. On the left, another piece of housing goes between the frame's cable stop, and another stop that's integrated into the front dérailleur, typically. Sheldon says one can get away with a non-stopped dérailleur, I think, but I'd have to check. I have at least one late 50s/early 60s English frame with this configuration around the BB, though it currently isn't built with a front dérailleur (3-speed S-A hub).

The OP's frame seems to have the same shifter braze-on on both sides. You can just make the non-drive-side one out in one of his photos.
Alex Moll's green bike above has a lever-operated "suicide" front shifter.