See here for role profile of balloon leaders:

Basically, being a balloon leader is a mark of respect and acknowledgement. My post was not really about BLs or whether they should be the default PLs. I'd actually say BLs should perhaps be the ones with the privilege of turning down being PL because they've done it before and we should avoid anyone feeling that playing PS2 is a regular chore. Also we have many people who have never PL'd. I'd really like to see more people trying to PL. If someone is over rank 20 then they've probably got enough of a clue how the game works to give meaningful orders. With mentoring they could probably also be good orders and given quite quickly.