According to some developer feedback from past updates the only thing we won't have is the start-up/shut-down procedure, everything else is modeled and works. However, a guy who had the chance to test the game in one of the shows posted his impressions and by no means does the lack of a start-up mean that it's a repeat of "press I, slam the throttle to the stops and fly" like it used to be.
In higher difficulty settings you need to turn on the fuel first, set the mixture and so on. It's as if the "start engine" key is just used to engage the starter and crank the engine, but we will still have to do a few things on our own.
So, with so many new controls, the question arises: "how many keybindings do i need? will i run out keyboard?"
This has also been answered at some point and they said you can do it whichever way you want. There's a clickable option, or you can just map it to the keyboard or stick/
HOTAS buttons.
Personally, i'll keep using the stick and keyboard for whatever is already modeled in IL2, which is the primary controls that are used in combat or other critical phases of flight: engine controls, fire buttons, gear, flaps, etc.
Then, for the rest of the advanced controls that don't require constant or time critical manipulation i'll use the mouse: setting the desired heading on the gyro compass, selecting fuel tanks, configuring the arming panels, etc.
This ensures commonality of controls for all the basic stuff in every flyable so it will be easy to remember, but at the same time it won't force me to memorize a million obscure keyboard shortcuts for the secondary controls...for switches and functions that i won't need in the midst of combat, i will just look around the cockpit and click on them with the mouse.