Being the GoF doesn't necessarily exclude the possibility that Carl is a Q.
Remember this scene from "Death Wish":
"JANEWAY: This was your existence before your confinement?
QUINN: I traveled the road many times, sat on the porch, played the games, been the dog, everything. I was even the scarecrow for a while.
JANEWAY: Why?
QUINN: Because I hadn't done it.
Q: Oh, we've all done the scarecrow. Big deal. "
Maybe one of the mentioned things was a symbol for taking the role of the Guardian...
Remember this scene from "Death Wish":
"JANEWAY: This was your existence before your confinement?
QUINN: I traveled the road many times, sat on the porch, played the games, been the dog, everything. I was even the scarecrow for a while.
JANEWAY: Why?
QUINN: Because I hadn't done it.
Q: Oh, we've all done the scarecrow. Big deal. "
Maybe one of the mentioned things was a symbol for taking the role of the Guardian...