I think Bradley should fight Alexander. I understand his team's position: the two Americans/the two best fighters shouldn't have to go after each other and have others try to cherry pick after they go to war. If they each take big fights, it will build up their names for a megafight. But boxing is about the best fighting the best. You earn paydays, you don't chase them. Guys like Floyd and Pac, and especially guys like BHop and the Klits earned their paydays.
But if Bradley fights Berto, that's a huge fight. The only reason people don't like it is because they still have questions to answer in their respective divisions. But that would be a huge fight and it would make more money for Bradley than an Alexander fight would.
As for Kahn, here's how he looks. Supremely talented fighter who got rocked by a heavy hitter (Prescott) and showed a suspect chin. He won his belt against a quality fighter who he matched up very well against (Kotelnik). Instead of fighting his mandatory (Maidana), he tried to set up a fight with a guy coming off a tough loss (JMM). When that fell through he went after the least dangerous big fight he could (Paulie). Even if he lost that fight, he wouldn't have gotten hurt. Now, instead of fighting his mandatory (Maidana), challenging the other champions (Bradley and Alexander) or avenging his loss (Prescott), his team is targeting a group of top fighters in the weight class below him who are tailor made for him (JMM, Diaz, Katsidis, Mitchell).
That type of match making is way too cautious. Outside of the names mentioned, there are plenty of quality fights at 140, and he's not going after any of them. Whoever he fights will do numbers, so there's not much of an excuse. It just comes across that he's scared or his team's scared for him.