Sponsored ads in videos are everywhere, and well delineated. Third party tools exist to skip them already -- and YouTube already has the data on where they start and end. They even show them on the timeline, although they call "end of sponsored advertisement" "most replayed"… presumedly because of everyone skipping the ad, losing their place, and then having to step back to try to find where the content begins again.
Here's how this could work. I would pay an additional $10/month for YouTube Scarlet. Content creators would have three options -- declare that their videos have no sources of revenue outside of YouTube revenue; provide start and end time stamps for any external-revenue-generating segments; or do nothing.
For my $10/month, videos in the second category would skip their promotion. In exchange, some portion of my $10/month would go to the video creator, just like ad/Premium revenue does today, and the metrics on number of videos where this segment was skipped would be made available in analytics for sharing with sponsors. Finally, I'd have access to a user preference to suppress videos in the third category for appearing in recommendations, ever.
Does this deal with every case? No. Would it make YouTube more pleasant for me and potentially others who share my values, without impacting current regular and Premium users, and with a neutral or positive impact on content creators? I assert yes.