Let’s go full guerilla: Plugin that lets you select the first and the last frame of an ad, thus allows to report the beginning and length to a synced database. When that frame is found in the buffer, skip X frames ahead.
For ergonomics, the plugin should be able to spot cuts in the video so you can easily select the correct frames.
For resilience, maybe settle for similar frames. Thinking about anti-abuse, maybe require a minimum number of reports relative to the views (and ofc allow to not skip stuff).