I'm in agreement with the critique of this. While, at first glance, putting a credit-buyable bonus doesn't seem too bad:
1. Eventually, if you figure out the gameplay, you'll be swimming in Credits. I usually end my test runs around 5 million and start over. There are lots of ways to get there now; you don't even need a Colony to get there.
2. Therefore, you're going to do it. To every single gun on every single ship. It's just a matter of grinding-time.
Now your fleet has significantly more damage potential; maybe it's not really 40%, because weapons miss a lot, but it's a lot higher than zero.
This is boring gameplay; the guns are all the same but now they're super-duper for no particular reason other than spending credits. You don't have to figure anything out and you don't have to have as much skill to play, just money.
3. Seriously, if you just want OP weapons, there are tons of mods here that offer that. Download them and enjoy watching all of the challenge of the game evaporate. This isn't Dark Souls; nobody will care if you've decided to play a mod and enjoy being a Space God.