I like the idea of Blaze being an observer, no matter the AU or continuity.
The beauty of his character is that he can be adapted into any of those without major changes. Neutrality works best for him; his core trait that is his stubborn independency conflicts greatly with any form of authority, be it Autobot or Decepticon.
So what does that make him?
He's a passive observer, with only minimal active involvement with either faction, mostly motivated by money and other business.
He is a courier. And a supplier. Whoever gives him the most amount of money wins his spark... For the duration of the contract.
You make sure to stick to your end of the deal.
That said, being an observer makes for someone who has his own opinions, seeing it all from an entirely different perspective. Should he meet someone with high authority from one or the other faction?
His opinions would have cost him life.