Sorry burst a bubble, but Fifth Gear, the last time I looked, is still alive (sort of) and shite, but on Discovery.
The problem any other broadcaster would have is that Aunty Beeb own the rights to the FORMAT. Anything else, with or without Clarkson, would just be a pale imitation.
Unless, of course, Aunty shoots herself in the foot and sells the rights to the format at the same time.