A decent weather depiction update with multiple cloud layers, cirrus and CBs (they are missing both with MSFS live weather and REX WF) that you have to actually get around of because of turbulence and microbursts. Basically the way we had it implemented in Active Sky products for FSX /P3D.

29 minutes ago, cianpars said:

All of the above would help improve the sim for me but moving trains would be nice too.  I guess that lenticular clouds and mountain wave would be out of the question.

Is it only me who finds that all planes still seem to skid a bit when turning whilst taxi ing a little too fast?

Then we would be well on the way to MS Train Sim 2 (third attempt!).

2 hours ago, Elvensmith said:

A purpose or career mode, built in not via 3rd party software and that supports resuming a saved flight. Essentially your own personal VA.

I am not sure it needs to be built into the sim but what would be great if there was a basic support for addons in this regard. Stuff like loading fuel, passengers and cargo (and the weight distribution) should be easily accessible by third parties as well as keeping track of wear and tear, persistent failures and such. Some of these work already through simconnect but not always reliably (fuel) and where it works it is rarely used by career addons for some reason. Since wear and failures are not in the core sim there is no universal way for career addons to make use of this. Landings and G-forces are accessible through Simconnect I think so that should be covered.