What if the investor is Riders father?
It has already been stated that Rider was adopted off the street by his dead mother, that he doesn’t remember his parents, last name, or where he came from.
Like burn and Lilly it is clear he went through the Mecha Gene experiment at a young age to save his life.
The investor for obvious reasons invested a lot of money into the project funding it completely as it seems.
People rarely do that unless the research will, 1. Save the world 2.Save their life
3. Save their child's life
If Rider was dying as I young child it stands to reason that if his parent was loaded he would give everything he had to make sure his precious son would be okay.
Other evidence
1. The investor was enraged when Gigi said she killed a mecha, but calmed down he learned it wasn’t Rider
2. If the investor was searching for Rider it makes sense that he found Gigi along the way
3. He said it wouldn’t do that Gigi’s face was burnt, if his son liked her (for her looks he would assume) it would be bad if she lost them
4. His “minons” write down names, he has them searching for them
5. Burns seems to have met the Investor, and was harsh against Rider when she met him
6. Rider has leadership skills, along with the investor