[Tuplanolla]

I wish to see

realistic start up procedures and optional automation for them (if the server permits it),
realistic fuel, oil and air management,
instrument errors and delays,
everything in first person (including climbing in the plane and bailing out),
pilot disabilities (like temporary deafness, paralyzation, hypoxia and loss of consciousness or blood),
no on-screen messages or graphics (like warnings, radio messages, compasses or maps),
flexible button configuration with multiple modes for each button (like switch/toggle/cycle or snap/pan/reset),
6dof without TrackIR or other equipment,
pseudo-random malfunctions (caused by stress, weather and manufacturing defects),
ricochets and failures of bullets,
speed-of-sound travel of sounds and shockwaves,
dynamic lighting levels to remove the advantages of gamma correction at night (the video signal is stripped of information instead of hiding it, which means darkness is pitch black or blurred),
debris inside cockpit (including shards of glass, oil and water),
wildlife and civilians (because there's nothing like hunting deer with rockets),
ability to move outside aircraft (after bailing out, even if the pilot is on fire),
campaigns (servers) requiring sticking with the chosen side (allies or axis),
online play (servers) requiring the completion of single-player training before joining,
disobedience and stupidity of ai pilots,
low graphics to enable massive furballs (hundreds of planes),
proper damage model (the cockpit can be torn in half),
custom ammo belt configurations,
percussive maintenance of instruments,
lightweight mission builder with good tools and hotkeys,
scripting language (like Ruby or Python) or a such for the mission builder and
wild arcade mode if there has to be one (flying an indestructible plane in a huge labyrinth with partially negative gravity could be fun)

in the simulator -- most of it only on maximum difficulty though. The features written in bold are very important; I won't buy the simulator if they're not included. Some of these have already been discussed, but I haven't noticed them being confirmed.