I think modernizing the videos is a good idea.
Personally, I'm hesitant to include modded content. I understand mods are very popular, and an integral part of the game for many players. However from a support perspective, it would introduce confusion and complications.
If we added modded videos, I would like to add some code to the game to not show those until after a player uses mods for the first time.

In any case, any videos would need approval by Keen, possibly through the media or art department(s).

If someone is willing to take up the task and produce some clips/videos that keep to the vanilla media style as best as possible, they can be passed along to Keen for approval.
Some style examples are the current ME videos, as well as the SE background videos.
Of course, this is only my recommendation for the best approval chances. It's possible any well made videos would be approved.

What about the new videos on the Steam shop page? Those should be added to the main menu imo

I remember suggesting the exact same thing when the forums were still alive.
Maybe a few players could also gather on a (vanilla) server and help make an entirely new movie, in an organized event like that one tournament back in the day!