He doesn't make sense as a backup because he can't run a conventional NFL offense. Teams don't have the time on the practice field to implement 2 completely different offenses.
He could be very good at running a Tebow offense, but no one is going to actually commit to that long term.
I actually think the arena league would be better for him than Canada. Faster, shorter, more accurate throws are required. The game is faster and simplified with the players on the field.