As I mentioned previously, Heroman seems to take a lot from Tetsujin 28, particularly with the idea of a kid remote-controlling a robot and using it to fight evil. However, I think there’s another series which draws a number of parallels to Stan Lee and Bones’ collaboration.
The series, or rather franchise I’m talking about is the “Yuusha” or “Brave” series. In the 1990s, Sunrise and toy company Takara created a series of super robot cartoons emphasizing the combining robot (and in turn, sales of toys based on combining robots). There was a new show every year from 1990-1997, with The King of Braves Gaogaigar being the biggest name. The two I want to concentrate on in particular are the first two, Brave Exkaiser and, particularly, The Brave Fighter of the Sun Fighbird.
In both shows, alien space police possess Earth vehicles in order to fend off evil menaces, which is at this point the most likely origin for Heroman in my opinion, particularly with the way the scientist in the first episode of Heroman sends his signal out to find extraterrestrial life. Similarly, in Fighbird a kooky scientist makes contact with alien life forms, including the aforementioned ghost alien cops, but also space criminals who escaped from a space prison (in space).
I know the similarities are pretty shallow, especially because Heroman is barely out at this point and hasn’t even established that much of its own story, but it really reminded me of those early Brave shows.