Have a Cup UI to be like crystals, so you can change them out for Defensive/Offensive any time and swap between for PvP and PvE. Keep the same items if you want to take them out from the "cup inventory" similar to crystal extraction. 
1-2b to swap around is kind've terrible.  

Edit: and now with forest fury barren from the market, uncupping takes tens of hours per cup

I would agree, the system is too punishing. Add them to the crystal slot UI and be done with it. 

With upcoming Karazad accessories I stress this even more

A few months ago i extracted the cup from the wrong accessory.... that was fun. 

Though i realised that I was better off not putting it back on and just wait until id get to changing the accessory the cup is for, which i did eventualy (it was a pen Tungrad, got a Pen Debo)

Recently i've been more annoyed i finally used the last free item brands i'd had for some years on my debos thinking WELL THOSE RE SAFE TO BRAND FOR THE NEXT FEW YEARS SURELY! And then Karazad....  I'd say they should allow us to recover those but lolol... That would mean less moeny for them so that's not happening. I think theyre just 250 Pearls each but still.

Anything would be better. You get locked in to either losing 3b+ now, waiting forever, or grinding awful spots that drop 1-2 an hour. This needs to be fixed.

This is still the same issue

No cup extraction event to be seen either