Certainly not the dumbest idea ever, but no I don't think there's anything really "there".
(note I'm a complete outsider as well, but have been following the Coyotes off-the-ice issues for what - 14 years now)
So here's a lit of the facilities at Legacy Park (taken from Wiki):
- 5,000 seat outdoor stadium
- 2,800 seat indoor stadium
- 35 soccer/lacrosse fields
- 57 indoor volleyball courts
- 8 baseball/softball fields
- 20 basketball courts
- 41 pickleball courts
- 12 beach volleyball courts
- 22 futsal courts
- Gymnastics center
- Dance studio
- Cheer center
- Sports performance center
So the closest thing would be the 2800 seat indoor stadium. That's smaller than Mullet arena, and doesn't sound like it even has an ice plant (no mention of hockey amongst any of the sports played there). To rebuild that as a 15-18k hockey arena would virtually mean starting from scratch. All of the rest of it would just mean a lot of extra headaches for the Coyotes and a business that is not successful at present.
And fundamentally - the Coyotes don't work as a stand-along business. Not in the short to medium term. If they did they could just go sign aa long-term lease at Glendale and be on their way. They need additional sources of income to offset losses - at least until the fanbase can grow enough to be self-sustaining.
The TED was going to have that additional income coming from the development right to the land. There's no development rights here.