I agree on the sprint function - this has been suggested several times

I think it could be implemented smarter using the suppression level. So that if you suppression level is full (yellow part) you will run at full speed, once you hit suppressed your speed will be reduced to normal speed and then again at overwhelmed reduced even further. This mechanic is already in place, it's just a matter of increasing movement speed overall - so no need for a sprint button at all.

The perk to reduce movement speed penalty for heavy weapons is a good idea, but removing it entirely would be bad. You can combine dual wielding pistols, to increase movement between fights if you want, but I get wanting to wield both a plasma and a flamer :D

And a perk to increase movement speed for melee/pistols would be fine too :)

A sprint option is a great idea, but regarding sprinting with heavies perhaps a weapon readying cooldown (1-2 second perhaps) after sprint ends before heavy weapons can be fired and a 5 second sprint cooldown.

Id like pistol and melee weapons to have an in sprint attack option with pistols having reduced accuracy and limited to the LMB attacks, while 1H melees have a slight negative to hit modifier but a slight increase in damage (say 10%). for 1H weapons I dont believe a cooldown necessary or warranted once out of sprint.

For non heavy 2 handers i.e. boltgun, lasgun auto etc I believe there shouldn't be a cooldown, but cannot attack during sprint but no delay for attack coming out of sprint either.

2H heavy should benefit most from an attack imo, during sprint perhaps adding something like a charging attack with 25-50% over base damage and knockback/stun effect but if used stops the sprint with a 5 second sprint cooldown and 1 second attack cooldown (or depletes stamina bar if one is used for sprint).