Top of my list comes:

(a) Re-sizeable, 2D Panels. (Important for forward visibility, and easy panel modifications)

(b) Cessna 150/152 Trainer. (For all the "would-be" Pilots).

(c) Full Screen toggle, Moving Map display, (also showing all Pilots in on-line Multiplayer Mode).

Paul....G-BPLF..FS 2004..FS Navigator.... ...!

One of the reasons I think M$ wants to have an integrated Live account is so that when flying online your system will automatically download any aircraft any other player is flying at that moment.  This would be the reason all the aircraft would need to be available on the Live system, but it would preclude anyone creating their "own" version of the aircraft, which would in turn mean that modifying flight dynamics and textures would be harder.  This also means that those of us intent on creating aircraft for it would be have a very structured and rigid set of rules we would have to follow as to what could be placed on the aircraft.  As such, much creativity would be lost, but we would gain some standardization as to what small parts were included on the aircraft.  In other words: no more "10k-poly gear parts"!

Again , Protect designers Work

Gmax---->Mdl---->3ds---->gmax again

Gmax----->Mdl
  like in the old fs9-FS2004 makemdl9 compilation

many well known designers prefers to wait the 45 minutes that takes to decompile using the fs9 makemdl and use this old format and still are using it for FSX

but its so easy to steal their work ,this to me was the worse mistake of all MSFS and there is a freeware software develop to steal literally Designers work 
,and if it wasn't unfair enough you can reverse the dds or bmp DTX 5 to 24/32 bitmaps and see and reinsert them in 3d max or gmax ALL in a single Same software
  this disencourage every one to do anything in this format
try to fix this please

remember People from Microsoft ,The successful of Microsoft Flight Simulator was that Not only people had a chance to feel like they were flying and airplane ,and people Plays a simulator like if it were a game ,Also Its because was a Game of design ..
  I don't fly it ,I don't Play it , I love to make airplanes more than everything ,and I'm sure that all designers would agree that this is another wonderful way to enjoy this Simulators..

and about Maya, Hell

NO!

  you can use any software to develop it ,but please leave the doors open to work in any Discreet develop softwares (3d studio max and Gmax)

You are doing great SeanTK by posting this ,because I'm sure that this are being read by people of Microsoft, I hope they Listen ,I wish Others designers from this site join me in my request

What I'd like to see is a nice collection of single and twin props (make and type doesn't matter that much) and a few jets. Not only Boeing, an Airbus or Embraer should be nice too.

Furthermore on the scenery department I would like to see the wind in the trees. Not the stiff poles with green textures we have now. And some ground that's actually soft. So when you skid off the runway, you'll need an excavator to continue your flight.

A maintanance mode would be nice too. No more Cessna's flying around with 10,000 hours and no oil change...

Carlo

Sloped runways for sure!  Anyone who has flown can tell you most runways are not flat, and that adds so much to the look and feel of an airport.  My home airport has a significant hill on the main runway, and FS just seems so flat.

As far as aircraft is concerned, I'd like to see more LSA aircraft.  Like an updated Flybaby, or CGS Hawk, Cessna Skycatcher, etc.  With the new Light Sport Aviation rules, I'd like to see it shown more on the sims.  Plus I'm also saving up to take Light Sport flight training.  I have found a few for existing sims, but not that many.

Like i've said I would love a C172P/N model considering the majority of the rental fleet consists of them.

More diverse textures/meshes would be nice to go along with areas.