>How do things like this usually work?

Totally fair. Except they probably don't want to copy line-for-line from Hijack, since all kernel code (including Hijack extensions) is GPL'd, and excessive copying from it to the player code might "taint" the closed-source player with GPL issues. But featurewise, feel free -- especially anything on the audio pathway like Bass, Treble, L/R Alignment, ...

The built-in VolAdj in the player seems to respond differently from that in Hijack, so the Hijack one stays put for now -- especially since Hijack is tuneable for one's own preference of response/attack rates. But if the player were to expose it's parameters for config.ini tuning, then we could nuke the Hijack version.

Cheers