I'm not exactly following you, and I'm new, so please forgive me if I'm misguided here. I do think the eq knobs should be able to be re-purposed.

My thoughts:

》Low EQ is the only knob widely used
》Hi freq. and Mid freq. could be used for stem volume

I would love to have direct control over vocal stems, to manually fade them in and out with a knob. I would suggest Hi freq. knob for Vocals, and Mid freq. knob for Melody (could be useful at times perhaps).

To expand on this, I simply think there should be a Serato setting in which for each knob (Low/Mid/Hi) you have a drop down list where you can select the function. And this list should be extensive, not limited, to allow for virtually any customization.

Thanks.

Since live stems was introduced by virtual dj some software let you choose to use the EQ knobs as a volume stem knob.

I suggest to introduce this feature & also to have a fast way to switch the Knob mode (virtual dj for example when i tested ask you to choose between classic EQ knobs or Stems knobs; if you want to switch you need to open preferences & select the other mode but this way will not be useful in live so you basically will not switch the Knob mode in live)

Hope you follow me now.