Something I would have loved to see, especially in this era of AI, is improvements to the ATC system. But it seems we're stuck with the one from FS2020, which in turn is largely the same it was 20 years ago.

Not everyone can or wants to go to VATSIM for realistic ATC coverage, but the default one is just dreadful. Obvious phraseology mistakes, happily vectoring you towards terrain, asking you to descend 20k ft. in 2 minutes, and the only way to communicate with it is via a list of pre-determined options.