Been running an idea for an adept character through my head lately, an adept who works as a spirit and para-critter hunter.
Anyway, since the distance strike power allows an adept to transmit an unarmed attack, be it normal, with killing hands, and even delayed damage. Would it be too unreasonable to allow it to be used to transmit an unarmed attack against a spirit when combating it via Force-of-Will?

I would probably allow it assuming one thing that someone else can probably confirm since my MITS is on loan: If the adept is rolling their melee skills and enhancing them with distance strike I'd let it work. IIRC, attacking a spirit as a force of will sort of thing you make a melee attack by the damage is determined by your charsima. Therefore, if the adept makes a melee attack with distance strike, then I'd let it happen. 'Course, I could be wrong on just about everything in this paragraph because I don't think that I've ever had anyone attack a spirit this way in any of my games.

My understanding is you only roll an unarmed or melee test if you can actually damage it with that form--ie killing hands, dual natured or weapon focus. Otherwise you would roll your charisma.

Therfore if your adept has astral perception and distance strike it would work. If the adept is relying on the spirit to materialize before beating it into next week, then it is just charisma.

Check out the Tracking power in Target: Awakened Lands for your hunter. It works even better with Astral Perception, which your character would probably need anyway to fight an unmanifested spirit.

For your adept attacks, maybe you can put an obvious geas on it, like Mortal Kombat's Nightwolf using axes and bows & arrows.

To quote the BBB pg 188