I have always said that only the Engineer should have access to the Fabricator and only one Engineer per game, this solves most problems, except, bad Engineers or the buying of Weapons and Grenades, but i would expect the easiest solution for the Weapons and Grenades is for the Engineer to be able to build an Ammunition Supply Station (limited to one only).
As for the bad Engineer thing, i would guess that the only way to sort that problem out is… Only implement that rule for 2nd tier games and above, it gives the low level Engineers the chance to level up and learn their Role. Of course, of the Engineer is a total Deek, nothing can stop that from happening.
And, i hate people that mess around and The Coalition should allow naming and shaming for certain instances, followed with a ban.