Yeah, I think they did. One doodad in sc1 of the twilight tileset looks to be inspired by space jockeys, and after watching Prometheus, I guess we could say seems like the doodads there have the same style in mind.
I'm kinda thinking Xel'Nagan harvesters would be like automated extractors that the player would deploy on a mineral field. There will be limited numbers of them per a building that can cast them.
My thoughts are that, the townhall of Xel'Naga would be called a "Core". It can spawn two building types: an Assimilator Node, and a Collector Node. A Core can deploy 6 Extractors for free, but this ability for the core can only cast 6 and that's it.
Collector Nodes will be able to spawn 3 Extractors at cost. It must be cast on a mineral field. Each Extractor will have a lifespan, and will expire, by which time, the Collector Node will have one more ready to cast. Extractors will behave like automated extractors, and will immediately add minerals to the player's resources.
Assimilator Nodes are built on Vespene geysers, and will act as automated gas extractors.
Cores can also construct 'Weaver Drones', which will transform into Conductors, where Xel'Nagan buildings can be materialized.
These Conductors are pads laying on the ground, and can spawn basic structures.
Players can then upgrade their Cores, to a Beacon. Beacons can be upgraded to Spires. I already have an idea for Spires.
Tech research buildings can only be summoned once the player has Spires. Beacons can summon Constructor Ships, floating buildings that can spawn units.
The Core looks like a Ring layed flat horizontally, above ground, and has a ball in the middle.
Beacons have the ball opened up and laying on the ground. Particle effects would show a stream of light shooting up to the sky.
Spires would then materialize at the middle of the ring, and the townhall will be in it's full form.