Does the king have to be in that planet to be counted if someone kills him/her? It does sound fun and amusing and surely new, im just alittle confused on how thats gonna work since we all hate players that always find a way to abuse that in some way. Other than that i like it. Heres an idea sort of similar to that.
"Planet Race Boost"
If your in the planet that your race is on you'll get a boost in your stats, still seeing this is a problem since there isnt many planets with those races being from it i still would like to throw this idea on there.