I think this pretty much says it all.
Probably the #1 quality in a head coach, for me, is who takes care of the division first. If Fewell can beat the Dolphins (check), the Jets (coming up), and the Pats* (the big test) -- especially with this crippled team -- then I would fully support giving him a shot at the permanent head coaching spot.
But you're right, if he can lead them past the Jets and then the Chiefs, even though that wouldn't exactly be a huge accomplishment overall, it would be setting up a huge playoff-atmosphere game for this team. Knocking off the Pats* at that point would get everybody fired up, I guarantee that.