So for 'bad guys' i give them an AI. The players know my AI, so they can game it on purpose, make plans, ECT.
I use individual initiative, and if the bad guy has to move first they make the most defensive move they can that gives better shots. So the charger will run 7+ or jump 5 in woods, whichever is the most defensive, while getting closer or in better position to shoot as a secondary concern... Thus they will jump to the closer heavy woods, instead of the heavy woods farther from the player.
If the bad guy doesn't lose initiative, it must move towards someone who has moved already, whomever they can get the best shots on. So if only a spider has moved with 3 marauders still waiting, the bad guy must move into the best range possible of the spider
This may mean not moving at all if they can't close to melee and the spider is within 7, as thats already the best range possible with stationary for +0. You can, if you lose init, force the enemy to show its back to your team if you move behind it for example, in a position it has to move to get you in arc by turning around. Its not easy to force the enemy to show its back, what with torso twists and backwards movement, so if the players set it up they earn it, cause of the AI rules. No GM "well the charger goes prone this turn so no one can shoot", as while that might be smart, its not fun for the players who now can't participate in the game for like 5 turns.
When it comes time to shoot, the bad guys must shoot their lowest numbers. So if the spider need's 8s to be hit, and that will kill the spider, a heavier mech stepping up that the bad guy needs 7s to hit will "draw agro". By the players knowing how to manage aggro by presenting the lower TMM/to hits, you avoid the very real issue of a GM wisely focusing down 1 unit at a time. Focusing 1 person down is feels bad for a multiperson scenario, so with my aggro rules the players are expected to juggle the enemy.
This means you can feel free to make the charger pretty deadly, like a 1/1 nasty piece of work, and as long as the players are playing smart their team of medium mechs/low end heavies/high end lights can win without you killing people too fast.