Will the sizes of the respective buildings change a lot? Or are they all the same size with just a different layout? If they are the same size, you might want to think Design Options (although that would be a lot to set up). If too complicated I would go with the linked files. You might want to set up 4 dependent views for each View and setup different titleblocks and sheets up front. Set up the print presets and it's just a matter of opening the file, picking the right preset and off you go.

If they are different in sizes it's a whole different ballgame. Live sections and details may be extremely difficult to setup so in that case I'd be tempted to use the second option (although I'm not fond of the non-live detailling)

How big are the villas? Are we talking a few sheets of details or lots of sheets? If were talking a few sheets, I would just copy and paste all the details into each project. I know you didn't mention that as an option, but it is the cleanest way. All your references are live, no printing issues, no issues with links. If a detail has to change it is pretty simple to copy and paste it back into the other projects.

My problem with the copy / paste is if the detail needs to be corrected, it will need to be corrected in all 6 projects and that could get hard to manage. I know we can group the details, then reload them into the other projects. That is the road we we going down, but I started thinking now that we can display so much stuff in the linked model. I could have much of the info in the linked model, set my views to show that, the schedules to read from linked models and have no real geometry at all in the "documentation project" The villas are very sim. in size, just slightly different layouts. So If I could keep all the live sections in the same place it might work.