I know some will say bad things just because they hate Cores in the game but the fact is you won't be able to get rid of them.  The planetary agreement part was added into relations and it is ok but also has it's flaws because of the players who use it.

I've been trying to get an alliance that expoed multiple systems of core violations to sort it out and accept the attack allowance with the planetary agreement thing but it either takes them a while or people propose the attacks but put it in the wrong way at times.  Just more complicated than it really should be.

What about just adding in the cores coordinates into a box when you set up the nap ingame and sign it.  Then the game itself can prevent you from entering those systems that are restricted for entry in the Nap agreement.  Give it a system like the current planetary agreement thing where it can be reviewed before the second family accepts to prevent someone from trying to put in a different core than was agreed upon of course.