If you are close to your HF, or on the same claim as where your HF is set, you get a small bonus (maybe 5% combat, -5% weariness, a small boost to stam regen ect)
If you are far away from your HF, or on a different claim, you get homesick and recieve a small drain on some abilities (higher stam loss, lower combat abilities ect)
The drain from homesickness could start out small, and grow over time, with a maximum that isn't crippling.
This would discourage vaults, and also provide a boost to defenders.
My rationalising behind this is that most people feel more comfortable in their home, whereas they are uncomfortable in other's homes, especially if they're doing something wrong.
Ideas?