We have implemented something similar in our new Mobile game. As an experiment. All inactive Castles disappear from the Map, so only active players stay. New players don't appear on the edge of the world, they appear where the whole fun and PvP is happening. I guess it's a positive thing.
However, it's a totally different mechanics, and implementing it in any other game would be very complicated. It would require a major redesign of some basic game features ans mechanics. And I'm not sure if our devs will agree to do that.
However, next week we're having a meeting with them and I will pass your suggestion :) Let's see what they say. Just remind Eugenia next week and she'll tell you what they answered :)