A long time ago I helped a young lady make a couple tables playable with just the "A" key which she had hooked up to a special controller that she hit with her elbow. She was an angel who was born with cerebral palsy. Her name was Yvette Yetter. We lost touch over the last few years and just now while looking her up to post something in this thread I found out she died in March of 22. Some of the old timers here may remember her, she went by the name Petunia. Yvette R. Yetter Obituary - News Journal (mansfieldnewsjournal.com)
Anyway, to get back on point here, a table can easily be slowed down just by changing the slope of the table. I would think some custom shaped triggers could be added to any table to make a sound when nearing an object and it could be separated right or left or forward and backward with existing sound fx built into vpx. Another thing that could be possible is ball audio tracking, so you can hear audible cues from the ball's x, y, and z positions, and even its x, y, and z velocity (speed). We already use these for ball rolling sounds and as mentioned even collisions on post and stuff could give audible cues. Only the developers working on the vpx program itself would be able to help make the editor more blind person accessible.
Another way of slowing the vpx program down that I know of is to download this cheat engine. Here is the link.
https://www.cheatengine.org/
Hope this helps. Right now, I think that you would be dependent on some authors of tables to mod tables to be blind person accessible. Sounds like you are very well equipped at doing things yourself, but shaping invisible triggers around areas of the playfield and scripting them may be something you would not be able to do.