I find this all quite sad really, he was one of the United greats, love him or loathe him, he hasn't had the messianic return he or any of us maybe though he would.
Seeing him lump it with the MLS or Saudi Arabia really strikes me as against type, it's his ego that stopped him going there already, and he clearly wants to play at something he considers the top level.
If I were him, and I can relate having flopped a trial at Swindon Town back when I was 15 of course, the consummate professional that I am... Call up Sporting, say "I want £100 a week, which I'll donate to charity, I don't mind playing a bit part, and I'd like to do my coaching badges with you".
For me that would be the fairytale, he doesn't need the money, and if you want to think about commercial and PR, it'd make you look great.