Besides a widget for the current sim rate an a dedicated binding for 1x, I have a suggestion for the implementation of higher sim rates.
I totally understand that higher sim rate above 8x or so are difficult to manage for aerodynamics and autopilot and stuff.
While higher sim rates are mainly interesting for long AP legs, the detailed system behavior is not important. Why not simply switch to simplified model with approximations for speed (against wind direction) and fuel consumption. I think you could go easily to 128x or even more.