One thing that's always complicated in gaming is when characters are much more competent at something than the players are. If it's something like shooting or swashbuckling, game rules handle it well: the player rolls dice, applies modifiers that represent the character's skill, and the rules describe the results.
If it's something like tactics, players can role-play it: "Getting through their armor at all is going to be tough, so let's concentrate fire, we three on their center-guy, you three on their center-right guy." Or they can abstract it: "I have Tactics-2, so I'll take the lead. Everyone add two to your initiative, and NPCs get plus two to morale."
But when you get to larger scales, the rules aren't all that capable of modeling character skills; players have to role-play it. "Second and Ninth Cohorts, lay down suppression fire. Fourth through Seventh Cohorts, charge two rounds, or three if your maniple commander sees fit. First and Tenth Cohorts, charge four rounds for flanking and encirclement. Third and Eighth Cohorts, charge one round, then take positions to take over suppression fire while the Second and Ninth pause to cool their weapons. Cohort leaders, any questions?"
Are those good orders? Darned if I know! I don't know how to command a legion of techno-Romans. Chances are that the person playing the enemy legion doesn't know either. So if I don't know, how do I play out the battle like my character is a skilled techno-legate? It's possible to abstract it -- give everyone a bonus to initiative and morale, but if it takes four cohorts worth of suppressing fire to cover a charge instead of just two, I'm still going to get smoked in battle.
It's also possible to abstract it further. Maybe instead of pushing around maniples on a battlefield, I just say, "I have ten fresh cohorts, each with four full strength maniples, and the First Maniple of each is Battle Hardened. I have Tactics-3." (Lots of dice rolling.) First Cohort, no damage. Second Cohort has a wounded Second Maniple leader but passed morale check. Third Cohort First Maniple is disrupted, and Third-Second failed morale. . . ." But that's war-gaming far outside the scope of Traveller rules.
Like MJ Dougherty has said, Traveller is built for a smaller scale than that. Stick to the right scale, or find war-game rules that work for the technology level you have in mind.
Or bring in a hardcore war-gamer to play the enemy colonel, and blast these over-powered characters down to size.