Sorry but I don't get it. The metric you're using like Top XXXX adresses can't really work. By switching from fixed 10BTX to 2,5% you are just doing the same as before without needing the current big stakeholders to distribute their coins to many adresses, which wasn't very hard because of the currently low transaction fees.
In my opinion you don't need to change the kind of payout mechanism. There has to be change in how to determine the "winners", if your aim would be to broaden the userbase. Are you discussing this internally?