In my opinion,abandon a block is just the same as didn't participated in mining a block,so odds won't change.
That's nice, but it is not a matter of opinion.
If I bet heads on a coin toss, then toss a coin, see that I've got tails and so throw the coin away and let you make the 2nd toss, don't you think I have a better chance of winning?
HH = win
HT = win
TH = win
TT = lose
I have a 75% chance of winning if I'm allowed to abandon the first result when I don't like it.
I like the idea of letting your players bankroll the site. You're a genius!

But the blockhash is the result of proof-of-work,you don't have a chance to make the 2nd toss.