Well, you have to remember that Metroid has Space Pirates refer to a certain species, which is the Zebesians. They're technically not even pirates, and Other M actually shied away from calling them Space Pirates. That's when them being called Zebesians began.

Anyway, plasma is not technically energy, since you're launching matter. However, I don't think all energy weapons should be off-limits to begin with, because energy weaponry is not necessary overly complex and expensive to make. For example, a Gauss rifle would be a very cheap and very common energy weapon. Railguns are a bit more expensive and rare, but are still going to be fairly cheap and common in any futuristic setting. I'd say Gauss railguns would be where the boundaries begin to get pushed a little, since they'd not be all too common compared to railguns and Gauss rifles.

And I thought we were all doing our own ships.