I assume you’d want the scripts to run right before playback starts, not on start.
Otherwise, updates (on subtitles, chapters, intro skipping, etc.) won’t be reflected on the video, since it would be already playing and the remote player does not get those updated mid-playback.
The playback would have to wait for the script to be finished before it actually starts playing. So this can potentially introduce a lot of delay. However, it’d be a good idea as an optional add-on.
Oh… ALL housekeeping? initially I thought you’d only want the video you are playing to be updated with missing extra content (subtitles and intro-skipper audio fingerprints).
Do note that if the library scan does not run, you won’t see any new videos that you might have added since the last scan, so you won’t even be able to see them in the Jellyfin UI to be able to play them. So at the very least, the library scan needs to run independently from the playback of any new video you’d wanna play that wasn’t detected in a previous scan.
It looks to me that it makes more sense to make it run automatically in a time range when you know you won’t be doing something important (I think you can tweak the schedule from the dashboard as admin). And perhaps combine that with manual library scans when needed.