Apart from the trust issue coinnewbit mentioned, there is another problem I can think of.
Each round needs 2 player at least to start waiting on the next block.
After a round has started people can buy tickets for that round till next block is found and then the round stops and picks a winner.
It may be hard to have at least 2 players in each round as a block is found in just 10 minutes on average, unless you have a large number of active frequent players.