This has probably been suggested along with METRA. It's time for Dovetail to go to the Midwest and Chicago would be perfect. If DTG or a 3rd party creates a CTA line I would hope they will get downtown Chicago and the Loop correctly. I would love to have the Red line in the game. I feel like we could get some scenarios that involve Cubs games. Below is the CTA map
For freight services in Chicago, there's a lot of short lines and all of the Class 1 RRs have trackage in Chicago. I'd love to see the BNSF/Metra Racetrack, a Canadian Pacific route in Chicago, or we could even see an earlier Milwaukee Road, Santa Fe, CB&Q, or C&NW Chicago route (or maybe PRR, Conrail, NYC, etc.). The Chicago "L" line would be cool to see.
it would come as a separate dlc since game development is long and complicated. But a license is still required