Problem: Since I foolishly extracted the map from the original terrain in a spherical shape, the map had limited room for expansion and looked a bit goofy at the edges.
Solution: Make a floating island "shell" and combine it with the original map.
Step 1: Create several hollow glass spheres, starting at the original map dimensions (200 block radius) and continuing until the glass is 5 blocks thick.
Step 2: Replace the glass with stone, whip out voxel sniper, and start extruding a natural landscape.
Step 3: Naturalize the terrain, start planting ludicrous amounts of trees.
Step 4: //replacenear 100 grass,tree,leaves,dirt sand . Repeat as necessary.
Step 5: //replacenear 100 sand stone. Repeat as necessary.
Step 6: Hollow out the interior, //flip up, save as schematic and add to existing map with MCEdit (good luck with the amount of RAM required to do this in-game).
Step 7: Floating Island!
Radius has been expanded to roughly 270 blocks - this new terrain will not contain water, and will involve a bit more terraforming.
As a question for the community - keep the vines are remove them all? I'm on the fence. While I like the way they look, they grow out of control and relying on them for pathways is not the best solution when players can destroy them at will.