Is this task a good candidate for Possible-Tech-Projects?

Suggestion: https://github.com/collab-project/videojs-wavesurfer

Can be built on the {T100106: Replace Kaltura player with Video.js} work that I have in progress (although quite a bit away from finishing that). Anyway, I think it's a nice idea for File pages, but i'm not so sure about transclusions.

My question on this front would be.. How to deal with this for the users who don't want this ? I'd rather not see ten thousand options and dozens of plugins only used by very few people.

Yes, the idea was mainly for file description pages, and I can't really imagine anyone objecting to enable it there by default (but, just in case of flying pigs, an RFC at Commons might be a good idea).

Of course it doesn't make much sense to use something like this in galleries, categories, "in-line" or anywhere else where just a tiny thumbnail is shown. There might be cases where it would make sense to have this in an article, though (things like bird calls, en:White noise or en:Bloop). Maybe it could be triggered manually through something like

[[File:foo.ogg|400px|waveform=true]]

Or triggered indirectly when the specified thumbnail size exceeds a certain amount of pixels. Or an additional button in the player that, when clicked, works like when you click on a video in an article (new "window" overlayed on top of the surrounding content, showing the waveform view with the surrounding content darkened/greyed out).

In some cases, a Spectrogram might actually be more useful, so ideally the user could switch between those two (freesounds.org has a button "change display" for that).