@spriggan02
I have toyed with that idea too, and I think it has merit, though I haven't come up with a truly workable solution yet.
@Airowird is right, you would have to scale up both income and fleet maintenance to balance it out, which would make occupying planets even less important.
The best idea I have come up with is not only scaling up output and cost, but time to reach the maximum level of output as well. A mining station could start with the same output and build cost as right now, or scaled up to make up for increased ship maintenance, but be upgradable which increases the output significantly. The mineral cost for that doesn't need to be all that high, I would rather tie it to time instead, losing one should take time to replace. If it takes 5-10 years to replace and upgrade the lost mining stations, then they are targets you will want to protect. You could of course take a doomstack and smash them one by one, but multiple smaller fleets would do it a lot faster.
The idea has its downsides though, long recovery times make vulnerable to successive declarations of war. Tall empires would have a lot fewer mining operations and thus would suffer much more from losing just one than a wide empire would.
I think one of the problems is that you have to stockpile and pay upfront for everything you build, but that's for another topic.
@Belaaron
The math is not wrong, yes a tiny increase has a dramatic effect on a battle. If one side has 10% more ships, they kill 10% more ships in the same time.
A has 110 ships and B 100 ships
A kills 11 and B kills 10
A has 100 ships and B 89
A kills 10 and B kills 9
A has 91 ships and B has 79
A kills 9 ships and B kills 8
A has 82 ships and B has 70
A kills 8 ships and B kills 7
A has 75 ships and B has 62
A kills 7 ships and B kills 6
A has 69 ships and B has 55
A kills 6 ships and B kills 6
A has 63 ships and B 49
A kills 6 ships and B 5
A has 57 ships and B 43
A kills 5 ships and B kills 4
A has 53 ships and B has 38
A kills 5 ships and B kills 4
A has 49 ships and B has 33
A kills 4 ships and B kills 4
A has 45 and B has 29
A kills 4 ships and B kills 3
A has 42 ships and B has 25
A kills 4 ships and B kills 3
A has 39 ships and B has 21
A kills 3 and B kills 2
A has 37 ships and B has 18
A kills 3 ships and B kills 2
A has 35 ships and B has 15
A kills 3 ships and B kills 2
A has 33 ships and B has 12
A kills 3 ships and B kills 1
A has 32 ships and B has 9
A kills 3 ships and B kills 1
A has 31 ships and B has 6
A kills 3 ships and B kills 1
A has 30 and B has 3 ships
A kills 3 ships and B kills 1
Result: A 81 ships lost, B 100 ships lost
And I rounded in favour of B, if I hadn't A would only have lost 70 ships.
You could call my rounding the tech advantage of B. Better tech only has a big enough impact to counter higher numbers if it increases the power of a fleet quadratically, so one level higher tech, 4 times the fleetpower, this is not the case and if you build a massive fleet of crappy tier 1 ships and send it against a tier 5 fleet with equal mineral cost, the T5 fleet just gets slaughtered despite the tech advantage. It's not just that, firing rate, damage boni, etc...if they together have a lower impact than the increase in numbers has, they aren't enough to turn the tide. It's pretty easy to try that for yourself, when the pirates spawn, try fighting them once with equal numbers and once with just 1 ship more, the difference is big.