what would be awesome to see?

Hi, and Yes, I'm a 3D modeler
Could be cool to create some heads, sure. Which ones?

I've decided to begin with Lee Falk's "The Phantom". There's some good resons why I choose him.
As far as I know, only one action figure of him has ever been produced and that's from the "Defenders of the earth" animated series. I always wanted an action figure worth the name of him growing up and finally I have the skills and means to pull it off Well, hopefully.
Another reason why I choose him is cause he's very plain. Basically just a muscular body so the sculpting would go fast and I can focus on articulations.
We'll see when I'm actually gonna start sculpting as I'm kind of on my vacation now and prefer to be at my workstation when doing graphics.

Another project I'm thinking of is to create a 59' cadillac ambulance with some sirens on the roof to fit 6" action figures.

You could probably make some good money if you sculpted 6-inch scale heads for characters who haven't been made yet, like that Phantom you mentioned. Also, you could sculpt the heads to mimic specific artist's styles for existing characters. For example, you could make Ariel Oliveti-style Punisher, Frank Cho-style Red Sonja (as seen on Queen of the Frozen Wastes covers), Rick Remender's Fear Agent, etc.

Making a 6-inch scale vehicle is ambitious! That would be a fantastic display piece.

Phantom sounds like a good place to start. You could even use that basic figure as a base to make removable accessories, like belts and armor for other characters.

Are you a 3D modeller? Because I'd straight up just pay you to make some heads to 3D print lol