The only relevant thing missing on the PCI bus is Intel 8237 DMA controller compatibility, correct? So how about a PCI sound card that contains an OPL3 chip as well as a virtual parallel port with a DAC that could be switched in software mode between Covox Speech Thing mode and Disney Sound Source mode?
Granted, the list of of DOS games that would support the DAC part of such a PCI card would be considerably shorter than the list of games that natively supported Sound Blaster, but with the help of proper Miles/AIL, DIGPAK, VESA VBE/AI and Sierra DRV drivers, as well as unofficial patches for some games, the number of games that would work with such a card would still be considerable. And that's just the DAC part. 100% Adlib compatibility at the hardware level would be easily achievable in a PCI card. As for OPL3 compatibility, in the case that the OPL3 chips had to be programmed differently on an Adlib Gold card compared to a Sound Blaster Pro 2 or a Sound Blaster 16, such modes could also be implemented in a software-switchable way, right?
Additionally, perhaps some kind of "hardware-assisted software DMA emulation" DAC mode could be implemented on such a PCI card. So that it would support the Sound Blaster I/O ports and IRQ 7 or 5, as well as ADPCM decoding in hardware, leaving only the DMA handling to be implemented in a software emulator. Would that be a crazy idea?