I think that instead of rolling dice, player should be allowed to select goods he want, amount of goods he can "take" should depend on relative raid power.
GUI will look exactly like normal trading with all possible loot listed.
This will fix all known issues with randomness of blueprints and decivilisation from overraiding.
If player managed to run raid with 10k marines, managed to wipe all deathballs and t6 station (with only one capital at time, with multiple capitals lost in process) he should get reward he want, instead of random "reward" (in form of vendor trash).
This also will fix save scumming issues.
To make things more simple, raid power should have conversion rate into credits and just use market price of goods.
If you have 2kk in raid power, you can take what you want, if you have 100k well, probably you will get only some vendor trash, but also you get exact values about how large your raid need to be, if you want "better" things.
If you reraid again and again, your 100k do not "accumulate" and such activity will never allow to get better things, just more vendor trash.