I'm sure it could be done. It's all open-source, whoever wants to take a stab at it is sure welcome to.
However, after the most recent updates to Hijack with the ability to tweak the voladj settings, I've found that Richard's code is quite good as-is and haven't yearned for anything more advanced.
My only problem has been trying to translate Richard's settings into the more-familiar-to-me compressor terms of attack, release, threshold, etc. His code actually takes a slightly different approach to it than a real compressor would, hence the differences in terms.
Before Richard's code was around, I actually tried running some music through the compressor in CoolEdit, and found that I couldn't get it to sound quite right. The "real" compressor was good for individual instruments, but didn't work well for fully-mixed songs. Richard's code is very transparent and "just works" on full songs.
Now... Having said that...
Something that's showing up as a common WinAmp plugin is a MULTIBAND COMPRESSOR, designed to do essentially what we want, which is even out the differences in compression between varying albums. If somebody implemented one of THESE on the empeg, then that would be rather cool and I would certainly want to try it out.