"Enhanced Strike Team" screams flexibility to me, and - frankly - the medium suit is the most flexible chassis.
Assuming IS tech, I came up with:
Ground MP 1, jump MP 3, 8 points advanced standard armour. Basic manipulators on each hand.
I didn't pay the spaces for modular mounts, so the first suit - the "BEST(N)", "Best'Un", or BEST Normal, is equipped with LRR in right arm mount, and an HMG in the left. Finally, for real flexibility in deployment, it uses mag clamps..
It's not meant to duel at long range - it can fight, but does its best getting up close & personal. (Unfortunately we decided not to let you mag-clamp units on the skin of VTOLS, support planes, ASFs, or DropShips ...)
The second version - BEST(E), "Bestie", or BEST Endurance, replaces the LRR with a David Gauss rifle, and the HMG with an SRM-2 pack with 5 reloads. Otherwise, it's identical. Obviously intended to provide fire support, but every bit as flexible as the Best'Un. A typical platoon would be three squads Best'Uns, and a squad of Besties.
Yup, the suit looks heavy-ish, but heavy, strike, and flexible don't mix well for my designs. And don't forget the David's enhanced damage against other BA, or its ability to load Infernos ;)