One of the biggest issues with Ambient Sounds in G/Q/ZDoom is that they ARE NOT flexible position-wise, most notably they can be heard in areas they are not intended to play in (thus making map editors vastly redesign levels to accommodate that or even outright remove the feature) and play the sound relative to their position (i.e they are quieter when the player is facing away from them) another issue is that having multiple sound actors in a map, especially a large one could cause performance issues) the addition could even ease map development somewhat, time spent in-and-out testing, and fiddling around with actor options would be decreased to changing the tab to an ambient sound, then testing, and ta-da, done and such a feature would help sooth these issues.
What I suggest to accommodate this is to add "Sector Ambient Sounds" ones that only play when the player (or even A player is in the defined Sector) and even Adding a new sector edit section that outright adds an "Sector Ambience" that reads from all the $Ambient defined soundsets.
Alternatively would be the suggested SNDSEQ method, which is extending Sound Sequences by adding a new Ambient action (which is constantly playing the loop which is only heard in the sector that has an ambient defined).