Currently, Level 2 User get 1 Power Stone each day to vote for their favorite. Equivalent of 30 Power stones each month free.
How about allowing readers with money and want to contribute to buy power stones. For example, $5 to buy 50 power stones. These paid power stones don't expire.
Vote using these "paid" power stones to support the authors/translators.
Authors/translators get a cut of these "paid" power stones. Free power stones don't pay out.
This could be like the Monthly Ticket ranking on Qidian in China.