Two principal fixes to the FF&S1 system which came up for discussion in the past were, alter the chassis/turret design sequence so that they are separate components with a hole in each (like Striker 1 did) this reduces the mass of the vehicle significantly and allows different armour on the turret from the chassis.
The other problem was the power output of the power plants which is too low for a given mass. Fix this and again the mass of the vehicles drops.
The biggest problem with approximating real world vehicles as FF&S1 vehicles come out significantly over mass compared to a real world equivalent.
I don't know what Mongoose and MM attitude would be to an official uprated FF&S book would be but I personally would buy such a book.
Antony