Considering if one faction owns the majority of the zones and have spent more resources to upgrade them, they would have to spread themselves thin and are susceptible to small raids. The constant collision of mega balls isn't the only method of combat we would like to promote variety somehow by adding a whole shit ton of things you can do in the core. I'd like the core to be as chaotic as possible such that smaller groups are given opportunities and activities they are capable of handling.
To create opportunities as such we'd have to create content to promote a more constant presence in the core and have motivation and rewards for staying in the core.
Also faction politics, power checking, defensive pacts, non-aggression agreement ought to come into play when hamster nests are in danger of being raided.