I agree with you to an extent, When Warren did the MItchell Katsidis show it was West Ham this and west ham that, The spectators were not even boxing fans but football fans. I think Khan can sell it out if its touted as a Bolton Wanderers + Khan + Reebok show. Just how Bob Arum does shows at the Cowboys stadium Hatton and GBP should ensure theyre is plenty of publicity ie having Khan and his opponent in Bolton Wanderers strips and doing alot of PR, On top of that get Reebok involved in a big way since they sponsor both Bolton Wanderers and Khan, Have reebok give away free t-shirts or reduced t-shirts. Also make sure the weather is good, the tickets are good value and the date for the fight does not conflict with a major football match in Manchester or nearby.
I agree in Britain no one will ever be big as Hatton was, and Haye is at the moment a bigger draw. But Khan's popularity can grow, he's yet to have the big hyped up match on sky, much like Hatton vs Mayweather was hyped up big time on all news channels. Then you had the David vs Goliath hype job, which turned Haye from a nobody into a superstar! If Khan has the right opponents and promotion then yes he can become probably the next biggest star next to Hatton.
If he is to big for the MEN then its Old Trafford or the City Of Manchester Stadium, the Reebok is to small to hold boxing when the MEN is a short drive away.
Thing is, as it is a night out most people will be drinking hence using public transport. Khan draws his support from all over greater Manchester. Bolton has crap public transport support, the train stops after 11. It's as much as £30 to get to Manchester on the bypass in a taxi (!). Even more for further out places obviously. Makes more sense to have it at the MEN which is easily reached by all.