They should have a betting system built in with escrow, where spectators bet on the outcome of matches in tournaments. {Sport betting}
I watch these tournaments and would also like to Tip the players {in game} if it was a GG. It's a spectator sport, and we should be able to bet on the outcome of these games. {Pro levels}
Blizzard could take a percentage of the bets, for the escrow service being rendered. {They like to make money on everything}
So on top of the prize money, people can bet on these games and the incentive for the Pro players will be to play better to get more tips.
To add to your perceptive post, if Blizzard or eSports events could somehow award prize money in BTC, that'd be good for all parties involved.
We're already seeing BTC tipping thanks to Changetip and Twitch for gamers livestreaming:
http://www.coindesk.com/changetip-integrates-with-game-streaming-service-twitch-tv/
Also, Xapo and CEVO with their partnership:
https://bitcoinmagazine.com/19958/xapo-partners-online-gaming-company-cevo-holds-21000-giveaway/
Looks promising on the gaming/Bitcoin front, hopefully Blizzard follows suit soon.
there was already some events with bitcoin prize as reward, they were showmatch between famous players(i'm talking about starcraft 2), like naniway vs scarlett(14 btc)
i don't know about other game