Don’t forget how important you said the captains were. Something like this would likely need a mentor in each group, also. If everyone in the group is there because they matched up as a 3/10 on skill, it’s all too easy for them to be stuck asking what are we doing wrong and either nobody knows, or worse, getting horrible advice from another 3.
Something like this would have probably kept me in this game for the last 5 years I’ve been gone. I think it would be awesome to be a mentor, at least for a while, if your guild breaks up or something. My nickname of sifu was because of how much mentoring I did in my guilds back when I was truly active in WOTLK/Cata.