Imagine if there were 8 or so servers, one stopped at each of the first 8 xpacs or so, and you can start on any. The server never moves forward, but you are always free to pay to transfer your character to the next server. Restrict players from ever going backward, but you can play at whatever stage you wanted.
While an interesting idea I don't think there is enough TLP population to really go beyond 2 - 3 servers of full pop. You've got Mangler running at high pop most of the day and now even Selo's is running medium pop on the server status screen in the mornings until the afternoons. I think if they continue to fix the TLPs to be easier to play on and see content for more players they'll increase the population slowly.
I tried to imagine 8 servers running EQ but could only see a mobile phone on a desktop running the 8 servers.