I took yesterday off to attend an important SCA event (I have other hobbies) and watched "Avengers: Age of Ultron" this afternoon, which means I'm really in the mood to take a look at Mechanon. However, I'm already committed to Classic Enemies, so let's keep going.
Mechanically, Firewing is pure power, a perfect example of the maxim "Points are for PCs." He's not built for cost effectiveness, with reduced END on his powers being the one concession to long-term survivability. Not that he needs it. His attacks start with a straight-up 12d6 EB, then get fancy (a 10d6 Explosion, a 10d6 Armor Piercer that's 0 END, a 12d6 Affects Desolid, and another 10d6 0 END blast that's also invisible). His defenses match up to these attacks quite nicely, and with a Speed of 7, he's got enough actions to make life extremely unpleasant for the heroes.
In all honesty, the biggest thing holding him back is his code of honor. He's obsessed with personal combat, single combat in particular, so he may hold off attacking an entire team in favor of fighting their fiercest combatant. This code, coupled with his arrogance, makes him easy to manipulate, a weakness his DNPC (a con artist named Jacob Lascke) has been known to exploit.
In my games, Firewing has been a fixture in the recent history. At least two campaigns featured "The Firewing War" as something that had happened in the recent past. I lifted it from the origin of Quasar, a nifty superhero published in Scott Heine's "To Serve and Protect," one of my favorite 3e adventures. In it, Quasar was a companion to Firewing (almost a Silver Surfer to Firewing's Galactus) who chose to warn the Earth of an incoming Malvan invasion. In my games, the Firewing War was a way to clear the superhero field a bit in order to provide room for the PCs to come in at a needed time. It was also Mechanon's origin, as a Malvan AI that corrupted an existing superhero team's robot butler and went rogue. It's still my preferred take on Mechanon.
See? I managed to work him in anyway.