Think up you've built one of those bad accepted maps some years ago, they says «Yeah, I like your map, it's a pretty cool one, the jumps are fun» and they accepts it. Now move some years forward (Today for example) and we say «Hum so after all, we are gonna removed your map, because it's a disgusting one», will you enjoy it ? I think not. Moreover there is some hours of works on some maps, and I will totally dislike if one day somebody say «We accept your map» and some years later, «After all, we renew parkour, we remove your map», a lot of hours of building who disapper without valable reason, it hurts.
About «Renovate some old maps», I've already tried and my map have been rejected for a relevant reason : «If we change the build and the parkour of a map, is it still the same map ?» ; even as buffing or nerfing a parkour can annoy the builder (I pick for example Wizolo with EiffelTower, which map judges ask us to nerf the map, I can't tell you how much he was annoyed), I can't imagine the player reaction if all the map is changed without his agreement ; just add it like a different map than the original then.