A long time ago, back before I was a playtester or had even attended Nationals (somewhere around 2002 or 2003), Cactus used to hold monthly card idea contests. I recall winning one of these with a card idea that was essentially a territory class-type card, but I called it a "brigade-dominant." Basically it was a dominant that could be played like a regular dominant except that you needed to have a Hero in play that matched the brigade of the dominant.
NAME: Plumb Line
TYPE: Brigade-Dominant
BRIGADE: Green
ABILITY: "Discard all Evil Characters in play with an unequal strength and toughness."
Obviously the ability would be a bit over-powered in today's game, but back then there were many difficult to defeat Evil Characters like King of Tyrus, Prince of this World and Red Dragon that ruled the game.
I recall getting a phone call from Doug Gray saying that I had won and that I could pick a pack of my choice as the prize. Of course I got a Warriors pack.
While I can't say that this particular card was the actual inspiration for territory-class, it definitely shows that card ideas can begin with players and eventually wind up as a card or mechanic in the game.