as i understand it the software that runs any mech has not changed much over the years so i do not see a reason why a specilised weapon system to exploit or insert itself into mech OS would not exist. infantry weapon bazooka warhead either attaches itself or punches through the armor and transmits jamming signal.
If punching through armor was so easy, why not just use a straight up explosive to disable the mech? Besides which, if BT weapons can't even guarantee what section of a mech gets hit, how the heck are you going to target the command and control systems?
And Operating Systems Don't Work Like That. Especially not MILITARY operating systems for platforms that aren't designed for remote control.
another warhead could take remote control over the mech itself...after all as i read it somewhere the mechs walk off the assembly line and do have some pre programed moves. another weapon could be called cluster jam shoulder mounted delivery system launching goo filled balls that attach and can pick up heat of the mech convert into electricity and discharge electric shock frying controls or connections that are not shielded...change ammo and you can use similar effect on the mob as riot control.
I don't think these techs even exist in BT. And even if the thermoelectric goo did, it'd be part of the mech's cooling system.
And you're still not getting past the armor unless you shoot it off first. And if you managed to shoot it off, then most of that other stuff you came up with is needlessly redundant, and likely more costly in money and mass than straight up explosive warheads.