The general consensus seems to be that currently, the Guard posts are not a threat, it's the ships they spawn as reinforcement waves that make them a threat.
In that case, give the homeworlds the same anti-hacking response mechanic that the SuperTerminal and Knowledge hacking have.
By this I mean once you kill your first core guard post, the AI starts throwing waves of ships at you as long as you have ships in the homeworld system (or the homeworld on alert?), but the wave size only increases each time a core guard post is killed.
This would count across both home systems, making the second AI homeworld tougher then the first. (At the moment both homeworlds are about the same difficulty, not counting stuff like the Avenger).
It also helps keep things interesting as this would be a homeworld (and hacking response) only mechanic.
I'm not sure how easy this would be to implement, I'm assuming since the base logic is present in the anti-hacking response it's not a huge deal to do.