they won't really become impenetrable choke points
all you need to do is place a nice shiny big fleet at the star, and smaller ones around the 4 - connected planets with a few gauss cannons and defense platforms and, wam, impenetrable fortress.
trust me, its an issue. mostly because in the 15 minutes it take one fleet to get between stars, you can already have built a matching fleet to repel them.
your opponent always has the option of sending his entire fleet to engage you at that location. Victory in these situations wills still come down to numbers, quality, fleet content and tactics....as it should be.
no, it will come down largely to production capacity, production capacity, production capacity, production capacity, and the slightest bare hint of higher level thinking in the defender. ah, almost forgot production capacity.
creating a force that is large enough to take another solar system, defeat a fleet, take a planet, defend that planet from counterattack etc. etc. is neigh impossible. its not enough simply to beat the enemies fleet
at the star. after that you have to take a planet, colonize it, defeat all of its defenses (of which there should be plenty), defend it from counterattack until you can get a serious defense going. I doubt even Sun Tzu or General Lee could do that.
Of course, if Ironclad doesn't create a Phase Space Interdiction ship, it will be extremely rare for battles to occur around stars
and why would you say that...
This sensor range system should also be used for star to star fleet detection.
already is, as far as I've seen.