I know there are many users who build badges for others, though it may be a good idea for the game to have a custom badge maker for building them yourself without needing to constantly make them manually on your later cars repetitively by memory. Here is how I think it can work:

1) Automation has an alternate creator option on the main menu which says "Badge Designer"
2) Entering it will give you preset parts to use, which includes original pre-made badges and Steam Workshop downloaded badge mods
3) Player will have a display to place the parts on, similar to how the Decal Creator in Forza Games worked but done in a way that is similar to Automation's Car Builder.
4) After player is finished building, it can be saved in the "Badges" section of the Car Creator and can also be posted in Steam's workshop (optional).

By doing this it not only makes it easier for players to make badges for themselves, but also allows more players to aid in creating badges for the community without running advanced programs. It's not a 100% replacement for using such advanced programs though, as there will still be limitations based on what you have in the Badge section of the game and you have more freedom making custom badges if you know how to use programs like Blender.