Are there any rules for battlesuits (think of the Starship Troopers novel) or mechs (as in Battletech) in any of the Mongoose Traveller sourcebooks? If so, where?
Battlesuits already exist in Traveller, and are what is called "Battledress". The Central Supply Catalog has some varieties of Battledress that expand the basic options somewhat.
Mechs can probably be built with the new Vehicles supplement, but I don't have that supplement, so I'm only guessing.