The only way we become a Republic is via sweeping Constitutional reforms.
Seeing as it seems (terrifyingly) that people here are OK with the Legislature having Executive power as well (i.e. writing laws for themselves to execute) we might as well just abolish all references to the GG and not replace the position with anything, and just let the Legislature do what they want with impunity.
What use is a President, if they don't have any actual powers? Why even have one?
It can be done very easily. We just combine the GG and the Crown into one single office, and give it a new name. Not really sweeping reform at all.
The last two points cancel it other out. If you don't trust the Executive and the Legislature to act honestly then we need an office with reserve powers. The new Crown/GG office can hold the reserve powers. Simple.