Personally, I'd like to see the US network moved from Arizona to Texas. Yes, there is a CA network for northern US people, but (1) southern states like Florida and Georgia still don't get good connection to any server and (2) CA is almost empty half the time, so playing on CA versus US isn't as fun.
Additionally, I'd like to see the EU servers moved to Italy or Germany. Though it isn't a big move, it does make a big difference in places such as Turkey and Romania, which takes up huge amount of our player base in EU. Besides that, it still offers a good connection to the UK and France.
With AU, I am not very familiar with anything so I have nothing to suggest for it. Another question out of curiosity, how many servers are there in the US?