I think autokicking from realm is not good idea. There are many reasons, why the player skip few days in the game. And find out that you've lost everything when you back - it's very very upset.
I had my own realm with max level of everything inside realm, 10k+ orbs and I was playing silence on my island, but today I opened the game and saw that I habe nothing now and because I was alone in the realm I don't have chance to back there.
And this is a second time. First time I was kicked from realm and I'm back but I lost time and forts and so on.
If the player is inactive, let's the realm decides to kick him out.
If the player is alone, let he plays to the end of the round if he wants so.
I know, it's team oriented game and alone player can't win and so on. But it's too heavy just take everything without any good reason.