bump
I went ahead and did this. It reads and writes using the normal BEX [PARS] table.
It was pretty easy, especially for Doom 2/Final Doom. Doom 1 was more tedious because of how the pars are stored in the episodic format (the zero index for each episode is a dummy time of zero instead of EXM1's time, so I have to skip that one each time). Though it's very possible I messed something up somewhere down the line that I missed so let me know if that happens.
As a sample, here's an updated AV.DEH with the hex-edited par times. This was made by loading AV.EXE and then saving its changes into a patch.
dhe_special_pars.zip