You can't game the system if you're getting paid by other users. We can argue about tweet quality, but it's no different than any other product or service that some people find valuable and others don't.
What you're describing is possible if Twitter agreed to pay top Tweeters to generate popular content, independent of user's volunteering to pay for that content. This would drive low-quality, low-effort content which nobody is interested in, but Twitter pays for anyways.
To keep scammers out they could start with restricting the feature to verified users. That would discourage beggars and hucksters until they work the kinks of admining and monitoring such a beast out.
What you're describing is possible if Twitter agreed to pay top Tweeters to generate popular content, independent of user's volunteering to pay for that content. This would drive low-quality, low-effort content which nobody is interested in, but Twitter pays for anyways.