I like the idea of giving him a two year long reign. That would have been pretty impressive during this time period. Not sure if they could have pulled it off. Though, only having 5 major PPVs a year instead of 12 definitely would have helped.
He definitely could have gone one year though, from WMX to WMXI. He still had a ton of momentum as champion when he lost the title at Survivor Series.
He could have capped off his feud with Owen at the Royal Rumble, and then dropped the title in a face vs face match vs the Undertaker at WMXI. If Shawn and Diesel were going to have their match at WMXI anyways, it didn't need the belt. They had their own history to build that feud around.
Maybe give Diesel a shorter reign after WMXI and then dropping it back to Bret so we could still have the epic Iron Man match at WMXII. Fantasy booking.