The feature has been discussed before, yes. I had a simpler, more manageable version of the idea in mind: Each song could have different amounts of bass and treble modification based on something in the comment field.

Mostly because I don't think most people want to painstakingly set up an entire host of EQ presets for each group of songs. I'd much rather just "tone down the bass for this album, tone down the treble for this album." etc.