It's true that Bill is the last possible guy they can bring back who will draw on curiosity, as Austin is clearly out of the running... whether they should is debateable when they have Kurt, Matt and Jeff and the like they can bring in.
If it's a one match scenario, Kurt probably offers more "bang for the buck" if it's coupled with a HOF induction. They can put him against Bryan in a "career ending match", if Bryan is to retire then there is little shame in it being against Kurt or vice versa.. The match can then be less bump based and more technical to cover both guy's problems.
Matt and Jeff, bring Matt back, have him win the title and Jeff returns to challenge him - immediate bigger impact than Bill.
Bill's first run was like Scott Steiner coming back in 02/03... you wanted to see what they do with him, how he stands up to the scrutiny and if he can really do anything of note there...Bill got a lot more favourable decisions than Steiner but the outcome was largely the same, the fans just didn't care enough. If they couldn't get behind Batista then it's highly unlikely they will for Bill.
The only way it makes sense is to bring him in as the heel, have Heyman turn on Brock and have them go at it one more time (and really go for it) Bill probably isn't up for that - it'd be a Warrior run from 96... run through some guys for a lot of money and he'd want "control".
Worrying thing is this is exactly how WCW started to go down the shitter - bringing in someone and giving them that control. Batista would make sense, he's a big movie star now... Jericho makes sense... Rock and Sting make sense and an argument could be made for Kurt and Jeff to have those schedules and they not detract...but neither would need control... Bill won't show up without it... and that to me is the biggest reason they should avoid this like the plauge... take the chance on this new Matt vs Jeff or even bring Punk back first.