It would probably be overpowered to just have to wander around a little and get enough machinery from Ruins to create a small mid-tier factory without doing any real work.

Suggestion: Ruins entities only yield raw resources when mined -- a minuscule amount, at that, like an Assembly Machine only yielding a few iron plates and a copper plate.

Suggestion 2 (ART!): Totally create new entities for the Ruins buildings to look almost identical to normal buildings, but change them to visually indicate their Ruined status, either by prettying them up with cracks and rust and dust and stuff, or a simpler making the whole machine a single tone of grey, or maybe some gray and red.