[mlangsdorf]

Antoni has written power-ups for a Mystic Knight - see Pyramid 3.60 "Mystic Power-Ups." So there's that.

As far as the Scout power-ups go, I probably wouldn't let a Mystic Archer take the extra Basic Move, and a Mystic Archer generally doesn't qualify for Bow Fencer, Double-Shot, Quick-Shot, or Strongbow. So unless you're already letting him take Heroic Archer, it doesn't seem like too much of a niche invasion to give him access to Enhanced Tracking and Telescopic Vision (along with a bunch of stuff he'd have access to anyway, like Extra Attack or Extraordinary Luck).

If you are letting the Mystic Archer take Heroic Archer, I can't see any reason to let him take the various Scout techniques/perks that require it. You're already invading the Scout's niche as the fast-moving ranged attacker with Heroic Archer.