All that incest would certainly change the gene pool. You'd have to go to a non-freak circus to see the normals. You'd have to buy your shoes in caterpillar, 10 left, 10 right. You might would have just left feet. No one would have to open their 3rd eye now that everyone has 5. Why worship Vishnu who's blue with 6 arms. You cousin, who's also your wife, is pink and blue striped, sports 8 arms and a leg. You get my drift.
I am not sure it would be like that, but it is perceivable that mistakes could be made with enough jumping around. I was just throwing it out there for something to consider.
Your grandparent from 30 generations back would only share a very small percentage of your DNA with you, thus it would be no closer a relative than someone in your home town who is a distant cousin because you share a grandparent from a couple hundred years prior. So I don't think it would create mutants or whatever. But I suppose it would still be pretty weird, ...would still be a potential morality/ethics issue.
If too many people made too many mistakes, what would happen to the general population over time? I suppose there would have to be a means of avoiding that, some kind of safe guard in place to prevent mistakes.