Rather than setting trainer sensitivity to 50%, 75%, 100% etc, would it be possible to use a similar approach as veloReality? Set it at sensitivity 1 up to a certain point and sensitivity 2 beyond that. For example, 100% sensitivity up tp 5% grade, 50% sensitivity beyond that.
That gives realistic feels for medium grades, while still allowing you to master steep grades without specialized equipment (granny gear…).
In this example a grade of 15% would feel like 10% (5% plus 0.5x10%)