Notice: This is not a request for a fully functional FMS, but for a more realistic looking FMS.
(Not my picture)
The FMC in IF is currently displaying GPS monitor, which I find very unrealistic. My idea is to let it display the flight plan ,heading and set altitude etc. Comparing to a fully functional FMS, this could be rather easy to implement (as we already have it in A350), and it will definitely add some realism to the sim.