What's stopping a player from getting into a group now and just going AFK? Matchmaking has nothing to do with people going AFK. If it was an issue, Bungie should be looking into anti AFK and Griefing measures, kick players not getting kills or moving,etc.
Change it so chests don't despawn when opened.
Yep, shouldn't be that difficult to make it so that a person who doesn't move for two minutes becomes bootable.