So I saw Unyielding Sentinel and Draconic Incarnation have been previewed today and while I'm excited to see the release notes it got me thinking about their possible builder/spender mechanics.
Draconic was the one where I instantly realised that there wasn't a great "builder" option in the current framework.
What does a fearsome dragon have? Aura of fear!
So make the "builder" for Draconic an aura that applies fear to enemies within 30ft and provides one Arcane charge whenever a fear stack is applied to an enemy at most once every 6 seconds.
Unyielding Sentinel could have a defence aura that provides a friendly defensive buff to self or any ally struck by an enemy and provide a martial charge whenever the buff is applied (every 6 seconds).
What other passive builder or spender options can you think of?