I'll give a practical example, looking at smurfy-net's mechlab I notice the Catapult A1 has 3 missile hard points in each arm, this makes the shotgun catapult possible, with 6 SRM6s.
Im not going to cry this variant is OP, my point is this:
each arm has 3 hard points, but the original loadout of this chassis' variant has an LRM15 in each arm, thats 15 launch tubes, so in my opinion, we should be allowed to use the 3 hard points until a maximun of 15 missiles, so we could use 3 SRM4 (=12) but not 3 SRM6 (=18). Get my point?
The Awesome 9M for instances has a sSRM2 in the arm, I notice when I put an SRM6 in it, it fires 2 missiles at a time to justify the ability to fire 6 missiles from 2 tubes. Thats just unrealistic, its like having an SRM2 with ultra fast reload rate. Instead it should limit to only SRM2 or NARC.
While im at it, AMS should be more powerfull, now that LRMs are fashio again, they're worthless. Perhaps the solution could be higher rate of fire, and a bit more ammo per ton, so they get a good chance of cleaning 75% of an LRM20 salvo (not two, that was an example) but will eventually run dry if there are too many boats. That would also make a good tactical choice in an 8-man group, to have for instances an Atlas K with 2 AMS and half a dozen tons of ammo to protect its team mates

And I think its unfair to have streaks completely useless against ECM, perhaps allow them to work only at very close range, or increase drastically their lock on time, making it a pain to hit those pesky ravens.