I don't really like this solution. It's not very clean
For my animator team I developped a marking menu depending on the selecton, type of object and custom attribute of objects.
I can thus separate different type of action with the keys.
":+clic" selection action (symetrize selection, select eyes, etc etc)
';+clic" action (symetrize selected, reset pos, etc etc)
This is my solution:
it's an old script and I can not put full but there was everything you need to understand how it work.
Updating is full in PySide. It is not yet functional as Maya markingmenu but that will come later