So why do not go the other way round?
At the moment a DHS has triple crits, same weight and 1,4 efficiency.
I suggest making a DHS
- double efficiency (its the name - more logical

- double crit (more logical (double parts) and the needed drawback)
- 1,5 tons (the advantage; coming from better (more expensive) material and some saved structure components)
That would mean you have a lot more logical and understandable DHS. It should also smooth balance problems I think.
Heavy and assaults are already very limited in crit space, a 2-crit DHS would make a "all 3 upgrade" Assault at least manageable while "capping" the amount you can put in with only DHS upgrade through the tonnage. The other way round you won't make a crit-free Slas Jenner or Hunch make 50% more dmg with DHS upgrade but only 1/3 because of the weight effect.
What do you think?