my suggestion for a siege system:
rams and other assault weapons can only be spawned at an idol and require materials and authority to spawn them.
-rams no longer get damaged by moving
-rams gain 10 tokens per hour and can store up to X many tokens
-moving the ram 1 tile uses up X tokens
-bashing once with the ram uses up X tokens (so if you barely reach the wall you may run out of tokens trying to bash! which means you have to stick around awhile)
-catapults when implemented could use up tokens per shot fired? etc
so basically you have to long trek with your ram and sneak it into your enemies territory or... build an assault outpost... maybe instead of spawning at an idol you can make an outpost which requires like 24 hours of drying as well but will let you get abit closer for your assaults?