You know, it's just possible that starbases, or any bases, are not the best option for defending a planet! The thing that was UNrealistic was the old SE II/MOO system of forcing you to go through the bases to reach the planet. It's quite realistic to be able to go around them as you can now.
Try satellites. Launch them in Groups of no more than 20 (I recommend 10, actually) so the Groups will be spread around and give better coverage. Increase the cargo space of all planets in the planetsize.txt file so there's more room for WPs. We have discussed this issue in the beta forums. There's no realistic limit for planet capacity. It's just a convention required by the game to have a finite setting. Ten times more cargo capacity for planets would not be unrealistic, though maybe the game couldn't handle it.
Maybe you could even increase the size of WPs then. If they were 400/600/800kt instead of 200/400/600kt you could have more efficiency. You might add a "Mega WP" of 2000kt for that matter and build your "ground starbase".