If we are to believe that Disney is unsalvageable by anyone living today, as the member I responded to suggests (edit: the parks at least), then why is selling the company in parts such a bad thing? That's the best shot of maintaining anything close to the "old Disney" and could actually turn out very well for the parks at least, if done right.
Disney is not Snapple, Mondeliz, Wendy's, Pepsi, or any of the other companies Trian has invested in. You cannot run Disney, an entertainment company, like you do food service or retail companies, which account for most of the companies they have invested in. They're vastly different businesses requiring different approaches.
In the absence of evidence as to how he would handle being on the board of an entertainment company, we are left to rely upon his public statements.