Simply eliminating income splitting while bringing the thresehold to 81k would probably provide the bulk of the savings. Bringing the cutoff to 100k from 185k would be the cherry on top.
That all said, you wanted some numbers, this researcher has provided some. Whether they are 100 percent accurate, I cannot begin to say. What I will say is with OAS barrelling towards 100b a year it would be nice to have some reforms to the program. If this can save 20b a year, all the better.