What would be really nice would be if hijack could make the dimmer avalable with a knob push.

The reason it's not on the knob push at the moment is because it's preferable for people to adjust it with the buttons. There is (was?) a hardware flaw on some mk2a's: turning the knob results in noise on the display connector, which corrupts the dimmer commands. This makes it hard to set the dimmer correctly by turning the knob.