Wow, this looks like one hell of an AMAZING MOD!!!! Just one minor suggestion, though, I'm of the view that Mass Transit might be better as a "Building", rather than a Civic. Maybe something you can add to a Neighbourhood district and/or City Centre to improve either the Housing or Amenity value of the square.
Other "Buildings" which I have recently thought of-especially for the later game-would be Freeways (increased gold, food & production value from Trade Routes), -1 Amenity, Housing or Appeal for the tile it is built on. Botanic Gardens (increased Appeal & Amenity), Park-lands (increased amenity).....these last two in particular would be Neighbourhood add-ons.
Anyway, just spit-balling. Fantastic work though!