I like where both Shadowhal and Annatar are going. The planet shield is a great idea and I agree that stations shouldn't be moving (except the unique vasari). As Shadowhal pointed out though, this will not be very functional in non-colonizable grav wells.
What about gas giants and stars? That little range we see now means the star bases are pretty much useless in those locations (except maybe guarding a couple neutrals). What would be better is if the range was increased so it took up about 50% of an astroid grav well. This would me you could funnel ships. So if they jumped in a gas giant, you could have your star base on the side that enters your space. Sure they could jump out, but getting into your next gravwell will be pretty hard if the range of the star base extends from the edges of the gas giant to the edge of the grav well.
If this range is too great though, or we put on phase jump inhibitors that completely stop jumping, we'd have a situation where attacking or hit and runs would become completely useless! We could no longer send a small fleet behind enemy lines to pillage and harrass the opponents economy. I know entrenchment is supposed to hinder these tactics because people were able to send in huge fleets to homeworlds and wreck them without any interference, but do we want to eliminate all pillage, privateering and raiding? I certainly hope not!
I'd also hope that we don't eliminate the need for a defensive fleet. If starbases can move and phase jump, then what's the point of having a fleet? Starbases will be far stronger and more effective than ships. So keep the range at a reasonable distance which still requires fleet support. Best to keep these stationary bases that are used for defense by providing planetary defense (big guns, planet shields, extensive range), and offensively by ressuply (repair station, production facility). Having it set up in an enemy gravity well to blow everything to bits is a bit redundant, we have fleets for that. Having a star base that sits in a gravity well just outside the opponents (astroid, nebulae etc) that pumps out ships for effective attacks or repairs for raiders would work well. On the other side, having a star base that can trap and destroy everything in a gravity well while removing all bombardment means we eliminate raids and defensive fleets.
EDIT*
Just read Annatar's new post. I agree with one statement fully and that's that we want starbases to be upgradable in multiple ways. Starbases shouldn't just be about defense (and offense) in a military sense. This is Sins after all and it's 4 times! Make upgrades "or" intensive, not "and" intensive. Have a star base that can produce units, or shoot far, or create culture, or be an economic boost. This is done right now through supply points (8/8). Which might work very well, I havne't had a chance to fully test it yet.