I would think there are plenty of ways to weed out people like illumi or hisoka from the exam. Say, if you do something which could potentially hurt a candidate then you are disqualified (hisoka would not have even been in the exam we saw if that was there). A background check would easily point out murderers and lunatics. I guess adding a few rules so that examiners could disqualify people based on their own opinion of whether they are dangerous to others would be a good idea but it would indeed need to be implemented carefully and with a number of restrictions. Adding a psychological test (not as a part of the actual exam though) would be extremely helpful. Overall the faction that makes the most sense winning is teradin's considering he does have a good cause in mind, does not seem secretly evil and has some support.
Not saying it can't be done, but it looks like there are a lot of people are in the Hunter's Association for various dubious reason to begin with. Sure you can have stricter tests, run harder background checks or whatever, but in the end the Hunter's Association didn't attract those dubious characters overnight. I'm sure he will make good on his promise but I think it'd be like trying to catch people dodging taxes or speeding. Sure he'll get some of them but it's something you can spend a lot of effort without much to show because people can just behave extra carefully while on the test, assuming the Association still retains its prestiege as the #1 organization in the world.
---------- Post added at 10:15 PM ---------- Previous post was at 10:04 PM ----------
Actually, if HXH was real, Teradin is probably the best to vote, because if HXH was real then you'd presumably know all the guys who ran for the chairman before promised big things but still just funnel privilege to the top, or got bogged down by bureaucratic stuff/infighting. While Teradin's ideals might not be obtainable he seems like a good guy who will at least try to do what he promised, compared to the other guys who promise big things but most likely will not make good on their promises.
But since it's almost certain whoever wins the election in HXH will actually change the Association in a significant way instead of just being 'another chairman', Teradin's prospects don't seem too great, because the winner of this election seems to be someone who will either do really good things or really mess it up.