So in collaboration with Trang, I've come to this combination of compromise & new feature.
By definition of a gaming 'Trinket' I would like to see the following
In the Avatar Equipment Panel, next to the boots an additional slot become available.
This slot would be for equipping 'Trinkets'.
Now I've already done a proposal for trinkets, but I can't be bothered to find it again.
Essentially the idea was to provide a new item that is trigger either manually, as a proc or is passively active without intervention from the wearer.
These trinkets would hypothetically contribute to battle by providing short boosts in capability.
Either via Burst statistics, survival statistic or CC [crowd control breaking].
Two examples would be
PvP: 'On use' remove stun/sleep/mute status, and provide immunity for 6 seconds. 35 second CD.
PvM: Grant yourself and allies 10% PvM offense for 20 seconds. 60 second CD.
There is a massive potential for customization on a trinket system when done correctly. However, Trang and I came to the conclusion that the King sets should be applied to this system as well.
The King sets [when turned in] would still provide the costume pieces.
Once the set is complete, you may redeem the set for a 'Trinket' containing the same bonus the king set provides. [same with Ancient Royal]
From experience, no one WANTS to be required to wear the King sets to get the bonus. But having it as a passive is also harmful to game balancing.
Having the Bonus become a 'Trinket' would require you to use the slot, for that bonus. And would NOT require [idealy] you to wear the King set. The costume would simply be a costume again.
I think this is a perfect compromise to retain the ability of the passive effect of the set, while giving the option to not wear it. Along with the many other possible additions to customization via a Trinket system [which doesn't require any graphic modeling or texturing, like the jewelry] and provide the requested results the community has been asking for.