BA missile launchers were specifically prohibited by the Ghosts of Obeedah rules.
Ah. I had only gotten to page 52 so far.
Still, rounding the missile weapons up to the nearest quarter ton turns them into 250-kg missile launchers, so a BA-SRM-4 would mass 1 ton. Not as unbalanced, but still better than Mech-grade weapons.
Making them fragile might be the key, where each pt of damage on a unit will disable one BA-scale weapon on the unit (starting with the BA-scale weapon that does the most damage). Area effect weapons would have to get some sort of bonus to this disabling effect. Doubling the rate might be an easy calculation, so a unit in the 5-ring of an artillery impact will lose its 5 heaviest BA-scale weapons first, then the unit takes 5 pts of damage and loses another 5 BA-scale weapons.
(Basically, take the damage -> disabled weapon rules from page 54 and make them worse. Damage to any location will damage any BA weapons, will damage multiple BA weapons each time, and the most dangerous BA weapons will fail first.)
Good use for the Pike vehicle, as it can plink away BA-scale direct-fire weapons from well outside their range.