Since there's a limit of 900k from center of the sun (IIRC) that means we would have problem with increasing planets to ship size.
Why not shrink down ships?
Nevermind the sun - planet distances, unless you want to shrink the planets too. But ideal thing to do would be to shrink ships, and if you want to take it a step further, you can shrink everything and jam two systems in one. Jump gates and everything still stands, only two systems are in the one system and that way you have more interaction per system.