Mystic pines is now a full function settlement, with caravans and shuffling settlers around.
Build really high up, on the adjacent overpass.
Works with DCMS, Better Settlers, SSEX, Snap-n-Build, and so on.
As far as I can tell it should work with any mods that work properly with the vanilla settlements.
I don't know if the Minuteman randoms will target it or not because I have those turned way down low, and it hasn't been called yet.
One just got called while I was playing. I was stuck in an interior cell and couldn't save them, but they successfully defended themselves (not sure if that's vanilla or a mod) So yeah, this is a fully functional settlement, even including the annoying shit.
If you find any bugs feel free to leave them in the comments.

Thanks to mods1984 for the Youtube tutorial on how to build a settlement hierarchy, I never would have figured it out on my own.

Recently I compiled a list of essential mods to get the most out of Fallout 4, and included this one. Check it out here: https://digitalfox.media/gaming-gorilla/post-apocalyptia-75-best-fallout-4-mods-to-get-the-best-fallout-4/