The more I think about it, here are my ideas for the starter scenarios. This is ASSUMING my thoughts on starter unit box of 4 Commandos, 5 Nightmares, 1 Mk1 Fiend (essentially half of black boxed set).
1) UNE is dispatched to investigate a mining colony/space station that went silent. Small assault ship sent. One half-section sent down/on-board. Runs into Nightmares.
UNE Forces: 1x half-section Commandos (Sergeant, 2x Commando, Heavy Weapon Commando)
Machine Forces: 5x Nightmares
Special Rules: like previously published scenario that escapes me (The Gaunlet?), Nightmares come back on board as replacements when removed. Make it turned based for winning? VPs? Get intel from command room and escape? Lots of options and variations...
2) Once intel is retrieved, plans to destroy (bombard) colony/space station is interrupted with assault on UNE ship by Machines.
UNE Forces: 1x half-section
Machine Forces: Nightmares + Fiend
Special Rules: Straight up brawl, nothing fancy. If Machines gets to bridge/control room, Machine win. Machines destroyed, UNE win.
Fluff, fluff, fluff...blah, blah, blah...can you prevent/stall the Machines expansion plans?
Map would be two-sided, with base/space station on one side and floor plan of UNE ship on the other. This can be the beginning of the rapid advance by the machines through the UNE universe (black box). They use the tech (or the whole ship!) from the captured UNE ship to speed up their expansion...
Just putting down ideas...