When you use /f power, it shows your power / maxpower. I have a suggestion with this. I think that you should not be able to gain power from staying at spawn, only in warzones / wilderness. I hate when people just stay around at spawn with tons of power. It would be more fair for the players who are willing to go out of spawn and build a base. It would also make powerful factions with tons of alts not so powerful since the alts can't just camp in spawn yet have 10 / 10 power.
I think the issue isn't that you can gain power, is that u can only lose -20 and you will only be able to raid noobs who set /f home. But that's just part of faction survival.