1. Damage Mods probably won't be gaining a penalty because stacking them doesn't give you the same potential for damage that it does now. With that being said, stacking 4-5 damage mods will bring the weapons back to the damage points they have now. Based on the January dropsuit stats, the only assault class that won't be able to stack 4-5 damage mods is the Amarr with 3 and considering that the Amarr have really handy bonuses for the Scrambler Rifle, the weapon best known for one-shotting, it's fair.
Stacking 5 damage mods is extremely PG intensive, and coupled with the PG consumption of plates and reppers, you'll have a poor tank to go with it. I'm not calling this balanced.
2. ARs, and a few other assault variants, faced one of the weakest nerfs outside of sidearms. They were nerf by 4 pts compared to the Rail Rifle which is 8 pts of a nerf, the ScR which is 7, and the CR which is 5. We went from 34 to 30 for our standard rifle...That's not that much of a jump in comparison to the others.
The percentage is far more important than the raw damage per shot. This affects DPS directly, and considering that ScR's DPS is already through the roof, it's not really a big deal. Don't forget that the AR is subpar at the moment as well. It's being nerfed from a lower base.
3. SMG is faster and the MagSec is slower. The SMG has less fitting requirements as well. It kinda evens itself out. In CQC, the SMG will more than likely still be dominate against a MagSec that's trying to rip you up in the SMG's optimal range. I mean, even now the SMG is one of the go to weapons for CQC.
AR is faster and the RR is slower. The AR has less fitting requirements as well... You get the picture. It's DPS at range coupled with the CQC capability that's devastating.
4. I believe they said the HMG is gaining some serious attention. WIth that said, if the HMG gains a nerf it shouldn't be to the point of uselessness. It should go without saying but many players would prefer to see it as a non-threat.