Giving additional bonus upon complying with the KYC is a good idea from Stake. Even if there are people who are afraid doing KYC, gambling businesses will still implement it because it is needed to maintain their licenses and also to protect their platform away from criminals. People don't need to be afraid complying to KYC as long as the website is reputable.
I do agree that it is not going to be easy to convince some people, you can tell many people that they will have to do KYC or they can't gamble here anymore and even that would not make them do KYC, they will end up just leaving. So, it's not an easy task to get everyone involved.
But for people, who did not have any reason at all to do it, just don't mind doing it but had no reason anyway, giving something in return means that they now have a reason and they were not against it to begin with but had no reason, and given reason they will do it. This is for those people and I believe that it would definitely make sense, and it would cause them to make sure they could make a profit from it.