And then, comes the guy that will end it all
After taking a look into more recent factions plugin configs, there is no way to make that happen.
It would cause Factions plugin engine to be modified, I don't have the source nor they (the plugin creators) distribute it.
So it's a no go. Sorry
I can only configure server wide power per player or raise manually each faction (will happen for premium users).
I will make owning land more costly than it already is, it will causes griefing to go down, since you'll have do own land and that will cost.
There may be other new things I haven't checked, but I will take care of those tomorrow.
Atm, there is still no 1.3 bukkit release.