I'd like to adjust the brightness on the fly to have a good level of brightness/darkness when needed. In the dark space I'd like it more calm and less distracting and in a bright environment or during action (combat, planetary landing) I'd like to have the holo elements very well readable.
In fact, the only thing I'd like to change is the HUD (bracket, crosshair, altitude readings, etc), while the dashboard I'd prefer to always be darker, because the dashboard elements have the solid dashboard in the background and are usually always well readable, while the HUD has always changing backgrounds. So I'd like to keep the dashboard permanently darker and adjust the brightness only of the HUD on the fly. But this would be too much to ask I figured, so I went for just keys/slider to adjust dashboard brightness as it is. Having separate brightness levels of the HUD and the dashboard would be great.
As for orbital lines. I also never use those. So having a separate key for this while no real use for me (although any additional control option is very welcome), while not the brightness which I'd have a use for, is kind of unfortunate.