Rose Gold Mongoose.
Rose Gold monsters could be rare encounters - like DQ's Metal Slimes.
Rose Gold Rock Star (star-shaped rock monster).
Rose Gold Pyrite (looks like a pirate of sorts - fool's gold pun?).
Rose Gold Thief Bug (they rob you blind and escape quickly).
Rose Gold Shark (*cue Jaws boss variant*).
The force ideas are strong with these ones. :3
I suppose having them as rare encounters could work, or we could have rose gold versions of each boss (except the final boss and post-game bosses). If we stick with enemies, all of them will be boss level in strength; if we go for bosses, they're as strong as the final boss (i.e Lv: 50). Defeating them drops an ultimate weapon for each party member.
Perhaps we can have equipment for each character and keep the pin system? If not, the Pin system should be able to stand on it's own. In either case, equipping your party members with a Pin allows them to learn skills from that pin; which can still work regardless if we have equipment or not.