I thought about this as well, but figured it might cause players who missed out by 1 block to scream bloody murder. Even if you know intellectually and logically that the rule is "fair" for everyone, psychologically it still sucks. (But I'm thinking about how people respond to games of chance in RL; maybe I'm misunderstanding the mindsets of crypto$ dice rollers?)
Actually as it would be a "continuous" lottery they would just end up with a ticket in the "next round" so I don't think it would be such a problem (the draws could be done daily or weekly I guess).
Now that I think about it perhaps instead of using the secondary hash (which can be altered by the forger) it might be better just to simply add up x time stamps from the following blocks and hash that (as a forger can't modify the time stamp by very much or they would end up creating an invalid block).
So given that the forger can only alter the time stamp by +-15 seconds (or it is more - am not sure about that) then at best they can decide which of 30 different values would be most suitable for a ticket that was purchased x blocks ago. It is still of some advantage to the forger who happens to be a player but it isn't a huge advantage (and you wouldn't always be able to predict that you will be the one forging the block x blocks in the future so you are still taking a risk by "buying a ticket").