Support. However, won't the transitions between old terrain and new terrain be really ugly? Also, the part about fish is very unrelated to the rest and should be removed imo. It's been suggested innumerable times before anyway.
This all looks restore it will need more than just rivers. My ideas that could improve this are:
- water mobs
- water falls
- make some biomes more common
There are ways of mojang doing these kinds of things. If they could look through mods with content they think would be good to add, then they ought to get the mod developers permission to add that to the game. I am sure they would get a yes every time.