Let's face it now,the idea for this was to make sieges and geopolitics not be the way they're now bur rather regional sieges and regional politics. CCNet N2 in the beggining had a good share of just regional politics and sieges but soon it became the way it is now. Start a siege in Antarctica per say and an Arab would find a way to intervene.

Considering the concept behind this failed,I'd say it's only fair to remove these limits finally. One of such cases is the siege on First Order,where Teutonic Order managed to siege American Syndicate despite being off the distance limit. Cases like this have occured frequently.

I'd like to mention that being far from the capital means you're far from your /ah. You'd say that you can borrow your neighbour's capital /ah for usage but thats up to the neighbour wheather they'd allow you to use /ah or not in a 1000 ways.

Last but not least.
Nations have colonies and colonies being far could bring trouble managing them. If a nation is strong enough to manage the colonies or if the colony somehow doesnt eventually split off from the mainland, then I don't see why they shouldn't be able to hold them. Say a nation in the Netherlands manages to maintain the Indonesian lands. You get the point. Being far can cause problems with logistics and maintance or even cause seperatism, so there isn't really a need to add a distance limit for nations.