You can actually finish the game with the Minutemen, using the Railroad only to decode the courser chip. And just how formidable the Minutemen are depends on you - most of their quests are settlement related, I got 28 settlements up and running with one of my characters. Now that should be enough people and a big enough presence to start rebuilding, right ? And they have the best imo hq of all the factions.
Here it is, my Castle, built entirely without mods, somehow I can't get them to work.. (all mods except for those that add new building options work fine). I only used one trick - settlements can't be too big, their size meter fills up very quickly and usually before you can build half of what you want, you can't build anymore. The trick is to scrap weapons
Sounds silly and it is- it's a bug. Simply enter the settlement construction area, throw away some weapons to the ground, enter construction mode and scrap them from there - each one will count as a scrapped building and will decrease this size meter slightly. And the scrap you get from them gets transferred to the workbench.
Anyway, here are some final shots of my castle, it might not be the most complex of the castles out there, but it is functional. I can't really show you the inside of "my house" as I've installed a mod that replaces all those dull original paintings with either classic masterpieces or.. pinup girls
So even though they are very stylish, google might go bat**** crazy over cartoon nipples on a game screenshot
..
The main (and only) gate, yet to be seriously threatened by any attack
Here's the courtyard, with all the shops, a crafting area and my house in the background. I fixed all the walls too.
A different angle shot that shows more details and a lovely garden/gazebo area in the back