Not to repeat myself too much from the Zereth Mortis feedback post:
I’m now at 30k cosmic flux and still have nothing to use it on, and it keeps piling up :> It’s starting to get worse than soul ash, I have almost 70k of that from more than a year of playing Torghast.
I think gear from “old” tiers would be a cool solution to this. Even if you don’t need the catchup gear or other useful items, you can get some transmog out of it!
I’d also suggest letting us trade it for other useful items. The item that lets us add sockets would have been great to have, for example, or perhaps you could trade flux for other currencies like anima, cyphers, sandworn relics, and so on? It would be particularly neat if there was a way to use it to help alts along, a renown 80 boost, upgrades to their covenant sanctums, reputation boosts, the list goes on and on.