same way u deal with commando with brens, but easier: sniper, explosive damage, tanks etc
Your solutions are how you deal with any infantry and by that measure, no infantry could ever be overpowered.
I dont deal with bren commandos because I dont ever see them, perhaps this is due to out of meta commander, or that brens just dont synergize with commandos.
Even if I did, FSJ arrive earlier, have better better vet, have a snare to ward off vehicles and are better at mid range while being on par(and better with vet) at long in terms of damage output compared to double bren commandos. The edge commandos have over FSJ is total HP pool. It should also be noted that they had the same edge over JLI but that didnt stop JLI from being overpowered.