Not only can the hosts not be duplicated in a Dick Sargent/Dick York fashion, the shows themselves have to be aware of each other and find ways to fit around what the other is doing. So, the uphill battle facing the localized versions of Top Gear is finding the proper personalities (the Australians already have) who will genuinely fit together and have chemistry, while also getting those people to do and say things that are compelling without just repeating the schtick of the original in a different location.
Wilman acknowledges that those who know about the original Top Gear in North America are fanatics who won't stand for a watered down retooling. Just because there may someday be a homegrown version of TG doesn't mean they'll stop watching the original. One thing that's skirted by Wilman's post is the writing. It's been said many times that the unvarnished opinion that flies on the original won't work on an advertising-dependent network like NBC in the U.S. If the presenters aren't given good material or allowed to riff with leeway, the U.S. Top Gear is dead in the water regardless of the personalities on camera.
[Source: Top Gear]