Scorpitrons are a core character/enemy in Wasteland! Just like Leather Jerks, Slicerdicers, and all the random encounter goons.
"nobody ever mentioned where they came from"
It's easy to think of Leather Jerks as WL's version a nation-spanning biker gang, like Hell's Angels, only more leathery.
"re-using special enemies like junk robots, who were created by one character is cheap recycling of assets"
This is true. WL1 had those robots in the Blood Temple, the ones that looked like a bunch of circuit boards on wheels. That's the sort of robot's you'd realistically end up with. And they went to the other side of the scales with the Threshing Crawlers and the rest of the Cochise robots. WL2's robots weren't too slouch (except for the disappointing version of Vax). Discobot was neat.
"how the f did they manage to get Scotchmo to Colorado,"
That man has the craziest "I got drunk and woke up the next morning in X" stories. I don't like Scotchmo, but I admit he totally fits the ol' 49'r, Crazy Prospector, Gabby Hayes bit you'd expect from post-ww3 Colorado. It's not all Mad Max punks, and nuke mutants. I hope they're inventive about the mutants, I agree WL needs some new goons to
go with the new territory. Give it some powered up 80s baddies like out of Thundercats. The more goons the better. And maybe we'll see some Serpoids!

"Actually, they were weaker than the Needles droids!"
Hmm, the robot police, perhaps? The Slicers could be handled by getting close with an ax. Especially the proton ax!