While these things have minor effects, they're effects are very impactful allowing for powerful combinations. Unless you plan to provide some way to easily earn GP (and I mean easily, not weeks of grinding for a handful of GP) than this mechanic is straight up P2W. Might as well add 1 shot kill weapons you can only get through the cash shop and call yourself Nexon.
If you're trying to find ways of monetization, the Elite subscription, cosmetics, hero ships, and boosters are enough. You can also provide ways for people to give these things to others allowing generous players to give them to players who would otherwise not purchase such items.