With the focus on missions and adventures, it will be inevitable that in the new sim we will see a lot of turboprop planes and turboshaft-powered helicopters. Therefore, it would be resonable to expect that the legacy FSX turboprop model be re-written from the ground up. The days where developers need to code their way around it to create something that behaves more realistically than a piston engine with sounds swapped should be gone. I wish our friends at Asobo would create a wholly new turboprop model that would be more flexible and could be used to accurately and believably (in another words: that from the cockpit it would look and feel like the real thing and could be flown according to real world techniques for a given powerplant) simulate:
- Free turbine turboprops (PT6 and modern turboprop airliners)
- Single shaft turboprops, both constant rpm (L-188, C-130H, MU-2) and variable rpm (RR Dart and other British turboprops) installations
- Single shaft turboshaft engines with clutch as in Aerospatiale helicopters (Alouette, Lama)
- Various propeller-related functions, like different blade locks (F-27 has 3 or 4 on its Rotols if I remember correctly), beta range (including “approach beta” on the Twin Otter and PC-6) and autofeathering
- Correct performance changes based on air density (altitude and temperature) and water/methanol injection systems as used eg. on L-410 and F-27 family aircraft
- FADECs and analog engine controls, CTOT systems like in the Saab 340
- Ideally, with failure and wear/tear system announced, we should have possibility to do hung starts, hot starts (on non-FADEC engines like on most older turboprops and helis like Bell 206), suffer a propeller runaway or dangerous engine vibration
I know It’s a detailed list and might sound a little bit entitled, but with the profile of the new sim that will focus on the other branches of aviation than GA Cirruses and A320 bus rides from LHA to CDG, It’s reasonable to ask for this I think. There have been some requests popping up here and there on the forums through the years, and MSFS turboprop simulation has certainly improved, but if there would be a complete overhaul, with the new sim that will go beyond anything any previous flight sim has ever offered, it’s the best moment to do so 
I hope we will be able to practice our muscle memory of button pushing during a non-FADEC start, or hear the screech of a Friendship’s RR Darts as it struggles from a high altitude airport somewhere in the South American mountains and see the green lights of water injection panel glowing as we pray for our performance calculations to be correct 
Sincerely, a turboprop lover