Regarding your suggested alternate contingency... again isn't that incorporated in your final reserve? (question!)
Now I know we should not land below final reserve. But what you are suggesting is a safety measure on a safety measure, double locks on your door, double redundancy. Is that warranted?
I don't know. Is Final reserve fuel contingency fuel or not?
I think using contingency fuel should not require a mayday. But using final reserve does.
It depends on how serious you consider a mayday due to fuel is.
I just find it odd that we take into account contingency fuel with regard to trip fuel which basicly covers for planning inaccuracy (wind, flightlevel, etc). But when we then calculate alternate fuel we pretend that these inaccuracies do not exist.