Mercer safehouse is supposed to be small place where synths can wait until railroad will find a good place for them.
That's what i made, a place for some railroad agents and for synths of course.
Also my builds:
Roman villa
Homeplate
Starlight Drive In City
Ten pines bluff village 2.0
Red Rocket Raider Outpost
Vault 88 The Last Hope Of The Institute
Croup Manor General's Residence
Oberland Station Minutemen Outpost
Spectacle Island Town
The Castle 2.0
Hangman's Alley Hobo Town
New Sanctuary Hills
Murkwater Construction Site Player Home
Tenpines Bluff Village
Counti Crossing Trading Post
Red Rocket City