But since Paula never received an upgrade no software was ever written to take advantage of better audio, so any upgrade to Paula would be a waste of time.
Oh, I dunno. I quite like the idea of a replacement that is register compatible with Paula but extends it with a few extra features. It would be cool if the incoming sample data was internally upsampled to 16/24-bits 44/48kHz, with optional interpolation per channel. In addition you could have a pan register for each channel. Digital output would be very nice too.
Even if all you had to start with was a global "mixer" tool that could bang these new registers directly to globally set the interpolation/panning of each channel it would be better than nothing.