Pete I have double grounded everything in my ETYPE since day one. I get your theory, It works but not even to put full current through the key, I would just scope out the prongs and see if they melted. Yes your right, But I wouldn't even turn the car on til it was rung out.
IMHO, The whole circuit as we have all talked about on other threads, in a series 2 is just HORRIBLE.
The 3w can, the plastic switch, current running through the switch, its an ugly set up.
Lets be honest its also 45 years old. The spring unit in the back always expands and burns up as well.
Hope it all works out.
Good luck.
GTJOEY1314