Back accessories have two slots: upper and lower. I'd like to suggest that front accessories be treated the same way. I can't think of anything that would be large enough to cause clipping and being able to wear a crest along with my barrel belly would be nice.
Speaking of crests, the crests earned as mission rewards should take the form of recipes or be sold by a vendor to players of sufficient rank. I don't see why Liquifier Crests should be unique and it'd serve as a minor crown sink.
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Personally I'd like to see the obscenely expensive end of auras be reusable on all the buyer's gear but that'd take pretty fundamental changes and people would whine about it no matter what. It's just a shame that you never even see the fancier stuff, you know?