I don't like how the corruption/crimson tends to spawn directly on top of my jungle during world generation. On the other side, it's a nice touch that by killing WoF you change your world forever. It becomes a battlefield for bizzare forces of light and dark, and there have to be casualties...
But hey, Terraria is meant to include terra-forming! You can dig out tunnels surrounding the jungle (or at least part of it). hallow/corruption kernels don't spawn in the jungle when you smash demon altars afaik.
It would be a good idea if there was dark green solution changing stuff into jungle, simple as that.