I think you should make clone packs for corps already in PC cost 80mil still and Corps not in PC 10-20 mil. You may worry about people abusing that system by making corps outside of PC just to hit a planet, but perhaps create a timer of a week for corps to enter PC.

Like you said, the barrier for large alliances to pay the 80 mil is not isk. So make them pay to have the "attack anywhere" advantage. I don't see many people utilizing their own districts for initial attacks.

Also attrition distance needs to be lessened a little bit. Like to echo the other guy that said there is no point to the chokes on the map if you can hit within 4 jumps at 100%. Example, those in egbinger can hit audesder at no penalty. So the fortification of your front lines is pointless.

I feel you need to have high attrition to start and higher percentages as you move out. So 80% once you hit outside current system then go 70%, 2nd jump, 65%, 3rd jump and 65%, 65% 65% 60% 60% etc. Allow people to still hit really far out, but at a reasonable clone cost, but still allow the ability to fortify your front lines.