Finally i soldered my own adapter and tested it succesfully
As mentioned, the important thing is, to switch the functions against the +16 V phantom power. The "ground pin" (pin 7) from the EVH's switching jack is unused. The control switcher must been set to "momentary mode". Even the FX can be switched perfectly on and off. At first, i wasn't sure if this is possible, but it is.
To switch the functions in the right order with the control switcher, i've drawn the adapter for everyone who is interested in build one. The buttons 1-3 switches the according channel and button 4 is for the FX loop. Please remember that the drawing shows the plugs when you look at it from the front.
I've been brosing looking for some info and found this to be most helpful. I'm looking for a way to get the Line 6 M13 to control channel switching on the EVH 5150 iii. With the midi out being 5pin on the M13, would it work the same as drawn in the diagram? Also, would it be at all possible to use the remaining to pins to power the M13?