Fuses would be acceptable as a link at the uk champs, I tech checked a couple of robots running this method and passed them last year.

Any locking mechanism to hold the link in, as you suggested should be fine aslong as you don't need tools to remove the link. If you have any concerns post a picture of what you've made prior to the event.

I personally have a swinging link door that pushes on my link, and the base of the link is mounted securely, meaning the link can't pop out if the doors shut. Been doing it that way since I built turbulence and I've never had a link fall out.