I use Levels a lot-it makes more sense to my brain cells. Have you considered adding a couple of more controls? Instead of three, five? This would allow adjustments in the “shadows” and the “highlight” ranges. As a side note, take a look at ACDSee Mac Studio or whatever they call it, there is a control there that is a different layout, but, to me, acts pretty much like a “Levels” control. What is really unique is the ability to select how many “bands” or areas you want to correct.
TIA