Lets give Thirion Ferocious Growth and Trailblaze it'd make sense since he's supposed to be this ancient guardian of the forest that emanates plant life around him it'dgive him some antirange since he has a horrible range of 2-4 on a large champion ( i can say honestly if thirion had 1-4 range or 1-3 range he'd be run alot more) and give incentive for people to run him in treefolk/plant decks because i have Never seen him once except in a werid kf/sl split with skywings any takers?
Range 1-x is extremely powerful too, you can bypass melee or ranged defenses at will with a single champ. I would say that 1-4 is worth more than 2-5 or maybe even 2-6.
what about instead of Ferocious Growth we give him vegetation veil 10 turn become vegetation (impending 1)