IMO Warpath retooled as Hardhead seems less forced than Darkmount retooled as Skullgrin. ;) Anyway, Universe Hardhead was never sold here, and the 3rd party add-ons isn't an option for those of us who only collect legit/licensed stuff. Seems expensive too.
I'd be satisfied with a Generations Hardhead personally. As for it not being a Headmaster, as Paulbot said, it'd only work if the original mould was a Headmaster. And besides, ROTF Bludgeon, Generations Thunderwing and Generations Skullgrin aren't Pretenders and not many people whinge about that. <shrug> Perhaps Hardhead simply never became a Headmaster in the Classicsverse, much like how he also never became a Headmaster in IDWverse (and Sunstreaker did!).
I personally would've preferred seeing Warpath repainted as Treds, but I guess that might be too obscure for the average casual collector. Could work as an exclusive figure (much like Games of Deception Bug Bite)