Proof-of-Pearl was a cute name for our lottery which was removed long ago. It was basically just random block rewards aka superblocks or whatever you'd like to call it but it didn't work out well.
It didn't work out well because each time you got a chance to stake a block, you could see what the lottery prize was going to be, and decide whether to submit the block to the network or not. You could calculate the threshold below which it was +EV to withhold the block. Submitting a block would destroy all the "age" on the staking output, making it very unlikely to stake again for a while, and so it was in your interest to withhold it and save the "age" for a better lotto prize.
Now, however, age is irrelevant. All that matters is the size of the output (other than the 510 block maturation period). So now I suspect that it would never be +EV to withhold a block, and so the lottery wouldn't be game-able.
Not that I'm saying you should reinstate the lottery, just that the reason for removing it is no longer valid, and so if you wanted to start the lottery up again, I think this time it could work better. I'm not sure most people would be in favour of it. Have a steady return from staking is probably more attractive to most than a lower regular return with occasional jackpots - this is why people join mining pools rather than solo mining.