If you could provide more specific information to me on what would be beneficial/useful to FOIA, I'd be more than happy to take a look, and likely send them -- and put them up on a public Github repo with a license that makes the data useful.
Email me -- arthur [at] dantonio [dot] co [no M].
jonathan [dot] j [dot] mason [at] gmail
Straight off the top, one problem is that transcripts aren't routinely generated, AFAIU. Yes, there's a court reporter taking down the proceedings, but what's generated isn't itself directly intelligible. Preparing an actual transcript from the proceedings for a small (2-day) case can run close to a thousand dollars. Doing this at scale would likely be highly expensive.
You bring to mind an alternative though: an automatic, random, appeal of a select number of cases to a review system of some sort. This might initially be a completely random sampling across all courts, but could then be subject to some sort of stratified sampling, with more cases subject to review from areas highlighted as problematic, and periodic reweighting.
That said, the records I've seen have been accurate.
Digital audio can be more difficult. Automated transcription sucks, and the costs for human annoyed machine transcription are very high.
Your AI solution would 1) tremendously reduce consts and 2) almost certainly remove a large share of the income of these independent reporters.
Mind: the problem could be resolved by making reporters employees of the court.
Get drunk and drive off the road into a corn field, well if you can get out without anyone noticing then no big deal.
One particular combination showed a 10x increase in correlation with charges being significantly reduced or dropped.
It would be very interesting to see a proper dataset and analysis on this type of information.