I have a last concern:
Simply,
I don't believe that the senate would be able to remove a controversial GM by a 2/3 majority. Currently, the left/right divide is 8/2. As I guess I will be defeated and maybe someone else, with the right likely regaining at least a seat for the next at large elections: in the long term, the statu quo will be 5 leftwingers/5 "rightwingers".
If the GM starts being controversial (that won't be the case for Kal obviously) and for example decides to raise unemployment rate by 4 points (yes it happened in the past), I don't think there will be enough leftwingers or rightwingers to cross party line if a 2/3 majority is needed.
That(s why I believe a 3/5 majority is more appropriate.