A while ago i had a mod idea but that mod would require one thing.
Is it possible to add a hyperdrive inhibiting ability to a STAR that covers lets say 90 % of a solar system ?
You can't add such an ability to a star, but since you have a lot of flexibility as to where you can place your starbases (which can have the ability), I guess it comes down to the same thing.
So far as range is concerned, you can certainly increase the range of the gravity well projectors beyond the vanilla range. My own mod (Research Unleashed) includes gravity well projectors with a hyperstop range of 5600, which is double the maximum vanilla range.
As far as I know, you can make the range larger, but I haven't personally tested the limits (this is something I planned to try for future versions of my mod). If you have the gravity well projector reasonably near to the star, then a range of 25,000 would be enough to cover the whole star. That's probably a bit much, and I suspect that a range of 15,000 to 20,000 ought to be sufficient.