Reputation systems re extremely hard. There are very few that ever turn out to be strongly abuse resistant (and there are other hazards as well, some already seen in the existing rep system, such as creating an entrenched system perceived as unfair or unwelcoming where those with high reputations are strongly favored by the rules at the expensive of those who are new or less well connected). Directly attaching rewards ups the ante significantly. I won't say it is impossible, as I rarely do, but why not try easier approaches first.