There already exists a spectator mode in PR2 thanks to @bls1999, but let's go a step further (if possible.)
How about the ability to specate any matches, even if you haven't joined them. Could be used for a lot of people, less skilled or don't have the patience, to watch an extremely skilled player complete a hard level/trap/frust, or for friends to watch other friends play the level they couldn't join in time.
If that feels too intrusive, there could be a simple password system to only let those in the know to spectate the match, or let it be only available to the friends of the match hoster.
How about the ability to specate any matches, even if you haven't joined them. Could be used for a lot of people, less skilled or don't have the patience, to watch an extremely skilled player complete a hard level/trap/frust, or for friends to watch other friends play the level they couldn't join in time.
If that feels too intrusive, there could be a simple password system to only let those in the know to spectate the match, or let it be only available to the friends of the match hoster.