I always know what kind of game I want to play, but it's overwhelming to set up, if even possible. It's tons of packages, forums, idk.. so I just end up playing vanilla, with maybe some rules among the players. But I wish there was a comprehensive interface to allow me to set all the stuff that I want.
From the top of my head (haven't played in over a year) it would be: cargo destination for people, cargo prices reflect proximity of other productiosn, mono/maglev only has passenger cabs, regular rail still gets upgrades, no planes I guess, "automatic" public transport within cities - no need to build stops, just buses driving around (transferring people to train stations). And probably more I can't think of now.