I think it won't be that big issue to pull the wires back, but now the issue is, that they are like they were glued inside the tube - no movement to either direction, not even slightest. Maybe I'll try with compressed air, there may be loose rust and dirt blocking them in place, unless someone with more experience can advice something better.
No pictures yet, but I can tell you that it is not a pretty sight.

All internal structures are gone from bottom to top of the sill, it was just patched on the surfaces, and quite badly. The rearmost connection of the auxiliary frame had been repaired for roadworthiness inspection so, that piece of sheet metal was hammered under the bushing, and "welding seams" were fabricated with sealing compound. It won't be much fun to fix that properly in my cramped garage.

So, the supports are pretty much completely gone, there's practically nothing left to patch, and new ones will need to be made.
The "center wall" of the sill will be renewed from the middle of front seat to the front wheel, and some 20-25cm from the rear, so the tube will not be removed. The ancient Tectyl-treatment has saved a lot where the dirt was not accumulated.