Not much else to say, I just really want a simple and straightforward "Combat Start" condition for one-time things like Ghost Heart Companion or other opening volley attacks that I'd rather not use more than once.

Alternatively, make it so that the reset timer is per encounter instead of global.  Right now setting the reset to 999 so that a skill will only be used at the start of the encounter doesn't work because the timer doesn't reset at the end of the encounter and will prevent the skill from being used for the next encounter.