If either Fred or Tommy win the primary, and pick the other Thompson, it will be Thompson/Thompson ticket. It’s not without merit. Tommy probably can carry Wisconsin (substitute for OH, which may flip to Dims), while the other Thompson can carry the South. If that’s the case, the Dims will use characters from Tin Tin comics to smear them (the movie may come out next year, BTW).
Wisconisn's 10 Electoral Votes can hardly substitute for Ohio's 20, but Tommy Thompson is probably the only Republican candidate who could carry Wisconsin. Even so, losing Ohio would make it tough.
As for the South -- sure, Fred Thompson could carry the South, but then again, so could every other GOP candidate except possibly Giuliani (who could still win most of the South -- maybe). Fred adds nothing to the Electoral calculus there, because our problem ain't in the South to begin with.
(this is not to deny that Fred may have some pull elsewhere, I'm just pointing out that he doesn't provide any unique advantage in the South)