I think the problem with that idea is the lack of the culture shock that has defined this show for the last two decades. If TAR had started as a show that only did one-three countries every year (like The Mole did; eg, "the Vietnam season", "the Greece and Cyprus season", "the Benelux season"), that might have worked. But it also wouldn't have lasted as long as it has.
Like that's an idea that could work (and has in the past; TAR Canada films domestically with a couple of international legs, and TAR China was originally a domestic race with teams of expats competing), but it wouldn't be TAR. It'd be one of those cheap knockoffs that used to turn up every couple of years trying to steal TAR's thunder.