In this playthrough the Railroad decided to use Spectacle Island for their Mercer safehouse.

It will be a waste of a big space with a lot of water just for the blasted safehouse.

Can I still use the island as a normal settlement? Anyone tried this?

Yes, you can use it and I did not notice any problems with it. I have safehouse at Jamaica plain, I sent 2 settlers there, one of them works in RR themed bar.

YA a safehouse works just like a normal settlement, like kitcat said... You can build and recruit to your hearts content, I have not yet encountered certain in game settlement synth/ false accusesed of being a synth nasty events ever at a safehouse, but that might just be luck not how the game was programmed.

The only problem is that if you ever turn the RR hostile, all settlers at the safehouse settlement turn hostile.

I had this as well, strangely though my settlement was on the east side of the island and the RR guy stayed on the west side of the island next to the ruined house.

Damn, I will have to go back and wipe them out then and begin again.

Thanks everyone for the informative replies

Love the idea of a themed bar - going to nick that idea.

On this playthrough I'm going MM & RR (there is NO good choice in F4), so I shouldn't get a problem further down the line either.

Thanks again.

Argh, so if I side with the Institute I'll have to put down the Abernathys at the farm? Will using the console to move the settlers out of the farm beforehand (and move them back after) solve the problem?

It should work with usual settlers, you can move them to other settlement any time. But with some named settlers... I don`t know. In theory you can make them "movable" with console commands. But I don`t know if it can cause any bugs with them. I did not try to do it. I accidently moved one named settler by assigning her to a supply line and then assigning to crops in her destination point. I just forgot what was her home settlement.