Need help with a particular PermissionsBukkit setup

Let's say I have 5 worlds. Worlds A and B share the same permissions. Worlds C, D, and E share another set of permissions. How would I set this up in my permissions file, without copying and pasting each list of permissions twice and thrice respectively? They're both quite long, and having to update the same list multiple times every time I want to change permissions for a group is asking for trouble.

My first thought was to move all my permissions to Bukkit's permissions.yml and then just have one permission node per world in PermissionsBukkit's config.yml, but there's a problem; there's no way to update permissions.yml without restarting the server.

Can anybody think of another solution? Thanks in advance.