Hi Tschüss, welcome to the forum. I'm sure your many skills will be useful for tinkering with tanks and I saw your other post about soldering SMD micro-SD card sockets, thanks.
As for the Scout, as you may know it is only a speed control (ESC) so by itself won't allow you to do much other than drive two motors, but for 1/35th scale there are much smaller ESCs that would be better choices.
I agree with you the TCB will no doubt be too large to fit into a 1/35 scale model. It might be just possible to fit one into a 1/24th scale model, such as the VsTank and FOV type models, if they are still sold.
Tamiya has a line of 1/35 RC tanks and you try to use those electronics, but I don't know if you can find them for sale separately, you may have to buy a whole kit and being Tamiya they are not cheap. There is also a company called
35rctank.com that sells RC conversion kits for various 1/35 scale models, possibly some of their electronics could be adapted. Finally
Clark lists a TK30 board on their website for 1/35 scale models but I don't know if the board is for sale anywhere.
For such a small model I would probably just control it via RC directly without any fancy electronics which you probably don't need anyway. Just an RC receiver, speed controllers for the drive motors, and program the mixing in your transmitter.