Disruptors were fun, but way too strong. If they returned now, they'd be even more powerful compared to other weapons, with red armor now being a thing. More shields for the bonus damage to work on. It was fun, but nah, I'd rather not see it return.
What could be fun instead though... Give Alternator the ability to equip either Double Tap or Select Fire, giving it the ability to shoot BOTH BARRELS SIMULTANEOUSLY, either in semiauto or full auto. Fire rate would be halved, which would keep the DPS intact. This would let it be more versatile, with the double shot adding some long range power. Double Tap would suit this better, but it depends if DT remains for Season 5 or not.
If you want to talk about a weak gun, the RE-45 could really use some love. Probably the worst fully kitted gun in the game. Even the Mozambique gets hammerpoint at least, though I'd honestly say fully kitted mozzie and RE-45 are about equal. I'd actually like to see the RE-45 being able to equip hammerpoints, but with a much weaker multiplier than the Mozambique/P2020. P2020 gets a 2.7x multiplier vs health (13 -> 35), Mozambique gets 2.27x (15x3 -> 34x3). I think the RE-45 could get Hammers with a 1.73x vs health (11 -> 19), which would put its DPS vs health below the P2020. And if that's too strong, maybe 1.65x (18 dmg).
Alternatively, make a new Hop-Up entirely. Maybe some sort of stun round that increases the slow on hit when equipped? Really hope it'll get SOMETHING with Season 5.
And a little off-topic, but... Mozambique should have a 6 round mag. Period. Doesn't even need anything else, since it has access to Hammerpoints, and it'd bring it out of meme status.