Hmm i have not really thought it through, i just took a long hard look at the planet and the action that went on around it and thought "damm this sure is a small space, with these 2 fleets nuking it out here it dont seem to be much room left" and then i looked out the window and up into the sky and thought abouth how vast space really is and even if a battle took place around a planet it would hardly be crowded even with hundreds of ships having a go at it. I dont really have any arguments beyond that it felt crowded lol. 
Logically i think larger grav wells would be better for larger planets, not asteroid'ish planets. Imagine a fleet orbiting our earth and then imagine one orbiting our moon, huge diff there, and as such the place around the moon would be alot more crowded. Hehe.
But as you pointed out there are negatives too it aswell so meh, i dont know. I just dont think the tiny grav wells do much justice to space as it really is. But hey then no game can be totally realistic.
By the way: maybe one race should have attack satelites as their orbitol weaponry. Similiar to satelites we use today just more sci'fied up. I dont know it just suddenly struck me as a nice orbital weaponry with a little charm. <shrugs>
Now a second thought struck me, what if a race could plant attack satelites in places now owned by them, i know some ships have that sorta allready but what if they could actually deploy it there, like setting up a blockade of weaponiced satelites around an enemy planet, blockading them, or cutting off a trade lane. It would need to be done by a ship abbility i reckon and that abbility would need to cost, more than normal prob. or maybe it could be built beforehand and then jjust released from a vessel and into orbit. Just a crazy idea, would make for a cool change though. Or hell it could even be a ship. Like a tiny starbase with no number cap. you build the "satelite" its initially eqipped with a engine to get it to its location or something and then you just build it when it reaces its destination, now it would need to have a cap in some way so either it uses your fleet cap or it uses the planets cap regardless of ownership. or, i dont know, just a crazy idea that came to me when i was writing this heh.
Also you know of the structure in distant stars that let your planet fire missiles at enemy ships, its like a controller that does targeting etc, would it be possibly to make a new planet build part that would be offensive in nature, it could say be linked to the planets population, and do less damage as the number went down. So if someone dont like beeing shot at from the planet, they had better start bombing it into oblivion, and say they get the planets health to 10%, well then the damage coming from the planet wil be tiny, simulating that the orbital weapon systems have taken losses from the bombardment, similiar to the population in itself, and similiar to the poulation growing back up, the weapons get rebuilt. Hmm hmm. In my oppinion this would help the stance that sins have taken where the planet is just a big dumb rock that just sits there, no launching figthers or missiles or lasers or whatnot from earth, no no, if we dont have any junk floating up there we are just totally helpless, no just ignore the hundreds of nuclear silos we ahve that are capable of sending a missile up there. Hehe. People should fear a planet! Not just use it as a toilet for their bombardment. Best would be if it could be different from planettype to planettype aswell. I picture more weaponry on certain planets vs others.
