tl;dr:
#1 A ponzi can only be fair if the operator does not play. This can not be proven. Great minds have tried for centuries. Go ahead and try it. I will applaud your success should you succeed.
#2 Whether or not dice sites and provably fair gambling can be cheated is not part of the discussion as it has nothing to do with ponzis
#3 Every time you give bitcoins to someone else, like the operator of any (!) site in order to do anything you are at risk of getting scammed. This is not an argument for ponzis. This is a general risk of the Internet.
1. Even if I assume that operators are playing, what is wrong with that ? The point is to cover the investment of the last investor and awaiting to be covered by another investor. I am not sure which ponzi game rule you are talking about. But, in my game, even operators have to wait for the next investor to be paid or they'll lose their investment. Unlike dice sites, there is no seed here that operators know. The only way a ponzi game operator can scam, that I can imagine, is running away with all the deposits, but same is true for dice site owners as well, especially those are accepting investments.
2. It is becoming part of the discussion, because no dice site owner is getting lebelled as scammer, but this is happening for ponzi game owners for being in the same business of gambling.
The operator play their own ponzi has no risk. Dice sites are not the same, they are proably fair. Stop repeating the same arguments over and over you allready know my answers. You just ignore the answers because you have no more arguments.
A ponzi is PvP, dice sites are Player vs House.