I love this feature request and it's crossed my mind a few times as well.
sharke
I think the trouble with the horizontal bar idea is that there wouldn't really be enough room on the strip to allow fine control of the cutoff of each filter. A separate knob for each cutoff would work though. They could probably also squeeze in a slope selector.
I think that, as long as the horizontal bar wasn't too small, and SHIFT to allow for fine control was employed, it would be workable while still having a small footprint on the GUI.