There are already mods out there that makes the would of Fallout 4 more "pretty". Just check Nexus.
As for a settlement mod I would like to see it include the following:
- Bug fixes so that placing walls around corners is no longer frustrating.
- All raiders spawn outside the settlement area so that perimeter walls can actually be useful.
- The ability to rename settlers.
- A "status window" that give you some info about a particular settler; like what job you assigned him / her to do; if any.
- More building parts like a wall with a doorway that can actually be placed inside a building.
- Walls with windows.
- Increase the max settlers a settlement can have.