QoL Request: Allow / prevent people joining a PF group based on mechanics completed

This mostly applies to Savage / Ultimate fights, and while simple in concept, it would be a massive quality of live improvement.

We allow filtering for any number of things, and preventing people from joining who are not ready to prog a particular mechanic seems no different in theory than preventing people below a certain ilvl or those who haven't cleared a battle from joining.

We need something more granular than just "has / hasn't cleared" as the bar to hit for more challenging content, if we all want a reliable way to gauge battle readiness.

And we need a way to prevent people who are well-meaning but think erroneously that watching a video is a substitute for having done the content from joining parties when they are not ready to prog that particular mechanic.

Signed,
- A player who's seen enrage in M4S and watched the above happen too often T_T

You can only practically do this for Ultimates and 4th turn Savages that have a checkpoint in them. Otherwise you're better off using third party tracking sites to vet the players that join.