Baro has a good idea about the budget. Right now, what is put into the calculation for whether a faction attacks you or another faction?
How much of your market share they are taking, right? What else?
The calculation should also include things such as:
How many gigantic armadas they lost recently
How many resources they have overall
How close your offending market is (vs hypothetical fuel cost)
Some variables or booleans in the faction file reflecting their ideology on free trade and aggression.
Maybe they're already there but constants need tweaking. But if you've destroyed a giant enemy armada, that should buy you some peace for a while (Skobelev's "The harder you hit them, the longer they stay down").
TAX/TREATIES: A faction could first try to extort monthly tax from you. Then if you pay even more, they'll send fleets to help defend against other factions. But it means you aren't earning much, and they might keep increasing the shakedown amount as time goes on, so that eventually you fight. Some faction file variables would make faction behavior more distinct form each other in behavior in this regard.
Basically, rather than having a bunch of repetitive expeditions from the same factions to the same colony, it would be a sort of story arc for each colony: You start independent, then get coerced into some kind of disadvantageous agreement with a powerful neighbor, then you get a "protectorate" status, then you get crushing exploitation until finally you fight.
With this system players can fight right away from the start if they want. But the tax option lets people avoid some of these repetitive expeditions. Basically, if you're going to have all these factions and economies, if they don't behave at all rationally, throwing away tonnes of fuel/money on repeated failed expeditions, it starts to feel pointless.