Sometimes you wish you have the ability to upvote a very good post multiple times. The same idea applies for bad posts.
To make it more controllable, we can grant such privilege to high-rep users (for example, above 10K). Also, the number of allowed upvotes/downvotes can be increased by reputation (for example, every 5K will grant a user one more extra upvote/downvote capability per post).
Another idea is to make it automatic. In other words, an upvote from a 10K user will grant the post owner 20 rep instead of 10 as opposed to other upvoters (below 10K rep users).