Quarterly clean-up
Game creators win because they save money on servers. They could merge servers after filtering out all the inactive players, effectively cutting server numbers down to 1/4-1/10 as many servers.
Players win because they get a more intense gameplay. I am surrounded by hundreds of inactive players, and yes it's nice to be able to farm them all but it is quite boring. I got attacked for the first time yesterday in 3 months. My lvl 10 towers are hungry for pixelated blood.
You could even host the PvP competition during these quarterly cleanups. If you have to shut the servers down for a week... Everybody could then have enough freetime to actively participate in the pvp collisions. Spread 3 months apart this won't ruin the market economy either.