There's one more chapter to go, but I've really enjoyed Coinciding Angles by Chokolatte Jedi. The fandoms are Stargate SG-1 and NCIS. It's soulmate fic, but it gets down into the weeds about setting up a police force encompassing Cheyenne Mountain, Area 51, the Antarctic site, and Atlantis. That kind of minutia is the kind of world building I love.