Currently over-revving exists, but it seems much too difficult to do, and it's practically idiot proof. You really have to TRY to break your engine.
Regarding radiators, I would like it a lot if DT allowed key combinations to open and close them. Right now, I have "R" set for rad flaps, and I have to tap repeatedly to cycle them. It would be nice to simply press R+ and R- to open and close them incrementally.
Secondly, it would be nice to have an option of manual mixture control. Currently pitch can be controlled by Shift+ and Shift- with Shift0 toggling auto/manual pitch. I use Ctrl+ and Ctrl- for mix, and it would be nice to be able to toggle auto/manual mix with Ctrl0. Finer mixture adjustments would be nice too, but I don't think the game will ever be able to model EGT to get a good "rich of peak" setting for cruise, etc.