I'm worried that if they turn Jeff Hardy heel too soon, they will lose the sympathy vote that they (specifically Jeff Jarrett) worked so hard to build up for his return. The crowd has expended a lot of emotion on Hardy, and regardless of the industry being "fake", the forgiveness offered by the fans was pretty genuine. Right now he is the most over person in TNA, followed closely by Sting and James Storm. They could easily turn him heel, but will the fans have the heart to "boo" him? When people have actually dealt with very "real" anger towards Jeff Hardy recently, supplementing it with "fake" anger for his character might be a very bad idea. I could be wrong - it may be brilliant, and maybe the fans will flock to booing him naturally. But they may also just stop caring...
Now, all that aside I think being a heel genuinely plays to Hardy's strengths much more than being a face does. He has a great tenure in pro wrestling, but it's no secret that he's not the smoothest mic worker in the business. He's had epic feuds, but for the most part it's been his opponents that carry the promo work. What Hardy has is his excellent ring work, ability to get the crowd behind him in a positive OR negative way, his extremely unique look, and his veteran experience. And let's face it...Hardy looked at his most bad-ass during his last run as a heel in TNA.
So another Hardy heel run? I could get behind that if they decided to go that route in... maybe a year? And I would LOVE to see this look return for him. He truly looks like an evil man - utterly sadistic. What I do NOT want to see, under any circumstances, is another Immortal run. Or any sort of evil, power-hungry faction with Hardy at the helm for that matter! If they absolutely must do it... turn him heel, give him (at most) one ally or manager that can speak for him from time to time, and allow him to cut loose and truly be the heel he can be. None of this wishy-washy cocky heel crap. Hardy is the type of guy that has to go big, or go home in everything he does, or it just won't work. He's just not vocally charismatic enough to ride the line between heel and face...
I will say one last concern of mine, and it may be a foolish one. I do fear that in the past these reality-based heel angles for Hardy have only enhanced his issues with drugs and other substances. Both the Hardy Boys are famous for not being able to distinguish that line between work and reality. It may be silly, and for any casual fan you may laugh at the thought of a character taking himself seriously...but Hardy is in a precarious place. When WWE pushed him to the sky, the pressure was to much, and he quit right before being arrested on serious drug charges. When Jeff was at the top of TNA for a short time, he ruined a PPV and caused a giant scandal. You don't want to give him too much responsibility, because I honestly don't think he's mature enough to handle it.