Is there any way to make a personal Waltheri for my own go games?
Where it shows win/draw/lose rate, how many times I've played a position, etc.

Or could someone make one?

You can use either Drago or Kombilo for this purpose: you add your local SGF collection, it gets indexed, then you can search a given pattern and you get results like in waltheri.
Later, you can update the collection by adding new games.