It already behaves this way if you aren't blocking ads. If you seek too far ahead in a video with mid-video ads, it'll show an ad before playing at the timestam

It already behaves this way if you aren't blocking ads. If you seek too far ahead in a video with mid-video ads, it'll show an ad before playing at the timestamp you selected. If they want to prevent ad-blocking, they can do the same thing except not serve the video ahead of time.