Really interesting concept! Are you planning on adding index fund investing in the future? It seems like you could incentivize investors to take a long term view with a similar, gamified approach.
That said, it was a fun idea. Instead of picking lottery numbers, ranking tickers in the right order, and then pulling a date out of a hat? Something that only operates on past data?
If you limit the savings options to tried and trusted savings vehicles - savings account, total bond market, total US market and total international - perhaps you can instill investment knowledge in the users on top of the good savings practices.