Most private servers host parties and such at certain times of day which urges users to get on around that time. So you could play real AVA when server is slow and when people start to get on switch to the private server. But if anyone is going to create a private server they're going to have to be willing to invest some money into a server and other things.
AVA is already dead. There's only like 500 people who go online at a time. Think about it, private servers are harder to find, and no A.V.A player probably has searched for "AVA PRIVATE SERVER". This isn't Maplestory, friend.