Surely, the gap is for a short range, powerful weapon? The shotgun (SG) is useful with either load until armour appears, and just about OK with light armour, because a 3 round burst of sabot is quite damage/TU efficient. The plasma pistol can kinda suffice as secondary weapon (at least you can blast away with it), but there isn't a decent ranged weapon to replace the SG. Converting the Plasma Blasters burst fire to Close Range would certainly help, but what's needed is more like a plasma SMG, with at least some ranged fire capability, but only really useful at close range.
I'm not sure the tables I used to look up some of the other values are correct, since they appear to be for v2.2, and I don't know if any really significant changes to weapons values have been made since that version. The principles would still aplly, even if the numbers need tweaking. Perhaps PHALANX engineers could reengineer captured weapons, and assemble a new one from pieces of one each of a Plasma Pistol, Rifle and Blaster. It would be available for research once all 3 base weapons have been researched, consumes one of each in building, and has stats similar to this
Range 18
5 - round burst 9TU : Dam 55 8 : acc 1.8 1.8 : crouch 0.8
Full Auto (10 rounds) 16TU : Dam 55 8 : acc 2.2 2.2 : crouch 0.9
Reload 14TU
Give it a one space, 10 round magazine, maybe have it use a remanufactured power cell too (consumes 1 of each other type to build, or two pistol chargers or something). No snap or aimed fire, the linkage to the power cell isn't refined enough to allow drawing measured amounts of power that precisely. It does more damage than an SMG or Riot Shotgun, but less than a Plasma Rifle or Laser Rifle (wave), and can't compete with the rifles on range anyway. It's not terribly accurate, so it needs to be at fairly close range to get enough hits to be effective against armour and / or tougher creatures, but it's limited to R18 anyway (between Plamsa Pistol and Rifle, actually less than an SMG and just about every non-shotgun human weapon)
With that damage rating (or thereabouts), it is useful against light armour, and does some damage to medium armoured aliens, and if heavy alien armour appears, I suspect it will need to be supplanted by a PBW equivalent. It takes slightly more TU to use than equivalent fire for an SMG, because it's inevitably going to be more awkward to use, but the increased damage, and reduced range keeps it competitive, without being overpowered.
Its' research requirements stop it becoming available to PHALANX until they *really* need it, because the aliens have to have fielded Plasma Blasters, and PHALANX need to have captured and researched one, and completed another research project all before they become available to build even. The same would apply to any PBW variant, so it would presumably be one of the last weapons you get in the game.
It even gives you something to do with all the alien crap building up in your storage areas, win-win
