I've been rather disapointed with most of the Traveller TO&Es. They really don't seem to take advantage of the incredible amounts of intelligence, surveillance, and reconaissance (ISR) capability and remote firepower that a 3I combat unit ought to be using.
Here's a sketch of how I'd form a heavy Imperial Marine infantry platoon (a Army unit would have a pair of tanks in the platoon, but only three squads and one command team. It would rely more on external ISR assets). These are big units, and they depend on having a high proportion of long-service troops (including veteran junior officers) to build the necessary battlefield awareness skills.
Command Element: There are two command teams -- one led by the Platoon Leader (a senior LT), the other by the Assistant Platoon Leader (a junior LT). Each officer has a senior sergeant supporting them. In addition to the officer and NCO, each command APC carries an operations team of one ISR coordinator, one fire support coordinator, and one communications operator, and the vehicle crew of a driver and a gunner/commander. The APC has up to two-dozen reconaissance drones run by the ISR coordinator, (plus the standard APC armament of a fusion gun and tac missiles).
Four Squads: Each squad has a squad leader, two 4-man fire teams, and a 2-man vehicle crew, and is mounted on a heavy APC. The APC carries a half-dozen recon drones that can be controlled directly by the squad leader or APC gunner (plus the usual armament). The squad leader is given forward-observer equipment and training, and would generally dismount with his troops.
At the tactical level, grav combat is so fluid that trying to maintain the typical two up, one back reserve just doen't work, so it's typical for the platoon to operate as two sections, each of two squads plus a command team. In mobile combat, the two sections work in overwatch -- one moving, one supporting. In occupation duties, the two sections would cover overlapping patrol areas, and each would be on-call to support the other as needed.
In addition to the platoon's organic fire support from the APCs, the fire support coordinators can call in ground-based artillery (including disposable rocket launcher batteries), ortillery from the Marines' transport ships, fighter support.
And they do use nukes -- small ones, mind you, but nukes none the less. They don't have the numbers to play nice against planetary forces that probably outnumber them 10 to one.