Haven't played through the quest but I've tried out the robot building a bit with one of my current character and I must say it's quite fun. It'll be perfect for my next playthrough when the survival mode goes into beta, building settlements with only robots ..
I've tried to avoid reading all the post so I don't spoil the quest but seems some have mentioned using the mechanist lair as a good base, so I presume it got a workshop in it to build inside? If so, is it like home plate in Diamond City or is at a fully functional "settlement" (doubt it since it's an interior cell but still nice to know)