More traditional triggers to me make the most sense coming off specific weaponskills, namely finishers with longer recast times. This is still working within the system instead of having an actual trigger mechanic though.

For example - Solid Barrel is a 5.0s recast timer. It generates a powder charge. 2.5s into its recast, Solid Barrel morphs into its Trigger OGCD, bypassing the GCD similar to old Empyreal Arrow.