Feature request: "minimum trust level" setting on a group

I have a “robust” political category on my forum whose membership is controlled by a group. Members can opt in.

We’ve had problems with new members joining this group for activist purposes. I’d really prefer it was a place for established members who understand the etiquette and accept the rules.

It would be really helpful to have a new group setting where I could restrict membership to a trust level (e.g. TL2 and above). Attempts to join the group on TL0-1 would receive a helpful message explaining that the group is restricted to established members of the forum.