Well, I think the intent is that the Welder provides the riot-power. So to me, the obvious solution is to push the Welder further into a riot-role. Buff its weapon, nerf its health, make sure that it can stand up to more raiders. Maybe swap out the pew-pew for something with better riot characteristics, but this might not really be necessary.
Then you don't have to cut the Welder's cost - riot-welders are more capable of doing naked-expands, which lets the Tank lab use Welders as the backbone of their opening force, plus a small Koda force to help "rescue" the welders that get overwhelmed or face Skirmishers.
The second problem with naked Welder expand is that welders can't repair themselves. If you sent out a Riot and a con separately, the con could fix the riot. The welder can't. And welders are too slow to come to each other's assistance - at the early-game, the welder
must work without other welders during the naked-expand-phase.
Now, the health-attrition of the naked welders could be considered a feature and not a bug.
But if it's something that needs correcting? I see two possibilities.
1) Give the Welder an idle-only regen (no moving, no working) to represent self-repair. I don't like this, the Welder doesn't need another "power", especially something as hard to see as self-repairing.
2) Zany Neonstorm idea: Give one of the raiders a weak nanolathe. This would allow the raider to (a) repair damaged Welders, and (b) reclaim in areas that are too far for the sluggish Welders to reach. We have a similar pattern in the Jumpy lab where it's difficult to cover much ground with Freakers so the Puppy helps pick up the slack.
Alternate approach, related to the discussion above about Levelers:
The Leveler and the Banisher are both tied to their labs - the models have tracks/wheels and that's not negotiable.
But that does create an interesting possibility. This might be a bit extreme but: Swap the stats of the Banisher and Leveler. Just scale the models up/down. Make the Banisher perform like a Leveler, and make the Leveler into a massive Banisher-scale unit. This way the LVeh lab isn't
completely reliant on the Samtruck to provide riot-power - it has the giant brobdagnagian mega-riot in the Leveler/Banisher. It also means there's
one heavyweight vehicle, just for funsies.
Meanwhile, the cute little nimble Leveler-banisher becomes part of the backbone of Heavy Tank gameplay.
Now, obviously you'd have to make the mini-Banisher weaker than the current Leveler, and the mega-Leveler stronger than the current Banisher - an arcing super-accurate missile is a more versatile weapon than a straight-fire cannon, and the stats should reflect this.
But otherwise? Swap them. The LV doesn't
need a light riot because it has the Slasher. The Tank lab could absolutely use one.