How about this:
This is done in brackets.
Round 1:
2 noobs versus 1 pro. Pro gets 2 coms so not really a disadvantage.
If pro wins the lowest elo noob goes to neighbour bracket. If the pro loses, the highest elo noob goes to neighbour bracket. (Alternatively pro decides who should leave if he wins and gets to chose who to take if neighbour pro lose.)
Round 2:
Noobs + pro versus neighbour noobs + pro. Losers get eliminated except one noob that is choosen randomly. (Alternatively the winning pro choose who proceeds(Alternatively the noob is sent to the next neighbour).)
Round 3:
3 noobs versus 1 pro...
Round 4:
3 Noobs + pro versus 3 noobs + pro... Elimination.
Round 5:
4 noobs versus 1 pro...
Round 6:
4 Noobs + pro versus 4 noobs + pro... Elimination.
If there are 8 pros and 16 noobs there are a total of 8 games where the pro faces 5 noobs in round 7 and the last game is 5 noobs + pro against 5 noobs + pro.