It's a forest. It should still look like one, not an open plain.
Think the existing zones with modern assets rather than comparing stylistically different zones. Drustvar and Duskwood are probably the only ones that work because the style is similar already.
- - - Updated - - -
You don't even need tech. Just replacing the model files. But unless the new asset has 100% the same dimensions as the old (at which point you're really just replacing textures), everything else will end up out of place. Even just replacing textures can make stuff look weird.
And that's ignoring that the attachment points are generally not the same. Replacing a tree will likely require manual readjustment so it doesn't sink into the ground or float above it.