^ This "building" would have to be very big (thus meaning you need a large amount of land or possibly an expansion base for build room) and most possibly have all tech requirement, with a VERY high price to build the scarab(s) AND the structure itself.
As for the building, I doubt it would be an actual production structure but maybe something along the lines of a...CCS Command Uplink, which may call down a scarab from an orbiting ship or something.

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