Actually healing units at stationary point is useless in this game, so I suggest Abbey of Kings changed like this.
●When Abbey of Kings is built it instantly gives Network of Citadels upgrade.
●When network of castles effect is turned off, (meaning the units are in the radius of network of castles but the bells are turned off) the units in the radius of network of castles are healed 4 per 1.5 second. it means the state when attack speed buff is gone.
It would be a defensive version of Deer Stone.