I was proposing using hashes of blocks from other chains to be the source of randomness for deciding which bets were winning and which were losing.

The Chancecoin protocol would have to be 'aware' of other chains.  Full chancecoin nodes would take as input blocks from Bitcoin, Dogecoin, etc..  Each full node would be capable of comparing the bets it received or sent (which are the transactions in the network, right?) against the hashes of the most recent external blocks received.  So each node would able to know independently which bets were won and lost.  That would make coming to consensus easy.

Maybe this is already how it works?  I don't even know if such a concept is compatible with Chancecoin's structure.