I will reply to this here, since this topic is more suitable for general stuff about the game.
Do not delete the accounts.
What about this idea:
Transfer their kingdom to the zombie area of the map. So the punishment for not being active is being relocated, but you still get to keep what you had, just in a different spot.
And assign their previous position in the map to newbies. So players who play a lot will be close to each other.
How do you handle newbie protection?
Inactive players have to be removed from the game, otherwise it will be totally infested with inactives after a while. Transfering to "inactive area" won't work for this game because here you have limited offices. An inactive player should not block an office...
There is no need for newbie protection because there is no individual PvP. The only combat is between groups of players (kingdoms). The protection of smaller kingdoms will be done via power/prestige difference (attacking much weaker kingdom yelds no reward).