This seems to me like crossing the line between adding variety and fixing what wasn't broken!
It's not about "fixing," because it doesn't replace the original. It's just exploring a new variation on the concept. If you listen to a movie soundtrack or a symphony, you'll often hear the composer reworking the same melody into many different forms -- one version of it may be solemn and sad and quiet, another intense and exciting, another light and humorous. The composer develops the possibilities inherent in the theme by transforming its presentation, but the core of the theme is still recognizable. This is how art works -- by exploring the ways an idea can be transformed and given new meaning.
Heck, it's hardly as if Hanna-Barbera's ideas were original to begin with.
The Flintstones was a direct copy of
The Honeymooners. Yogi Bear was an Art Carney impression. Huckleberry Hound was an Andy Griffith impression, Snagglepuss was a Bert Lahr impression, etc.
Scooby-Doo was invented as a knockoff of Filmation's
The Archies (they were originally going to be a music group, an idea H-B did use in later Scooby knockoffs like
Jabberjaw) and its characters are pastiches of the cast of
The Many Loves of Dobie Gillis -- Fred is Dobie (Dwayne Hickman), Shaggy is Maynard (Bob Denver), Daphne is Thalia (Tuesday Weld), and Velma is Zelda (Sheila James).
As for
The Impossibles, I never saw it, but Wikipedia suggests it was a knockoff of
The Monkees (and the Beatles) with superpowers added. Wikipedia also says that the concept was recycled in H-B's later
Super Globetrotters cartoon, a reworking of their
Harlem Globetrotters cartoon that gave the Globetrotters super powers. Apparently they copied the Impossibles' powers exactly and even retraced the same animation sequences for the new characters, Filmation-style.
So I'm sorry, but to defend Hanna-Barbera as some sort of pure bastion of originality that should never be tampered with is ludicrous. Most of what they did was the result of copying and transforming other people's ideas, or simply recycling their own used ideas in a slightly altered form.