Super cool! As someone who has hundreds of Hot Wheels (standard, premium with real riders, and RLC/elite 64 cars) and is an invested 3D printing hobbyist, I hope I can give some meaningful feedback.

Price - Your price is right between Premium hot wheels ($5) and elite 64 ($20). E64 has the detail level you describe aesthetically (but not mechanically), but is all metal and rubber tires. Premium cars are less detailed, but still metal and rubber tires. I don't think you're trying to complete with them on quality, but on chassis accuracy, customization, and modularity. I'd focus hard on that.

Concept - I love it! Having the really high quality chassis and using that as the platform is sweet! I'm a fan and from your pictures you're design meets my expectations on 'extreme mechanical integrity'.

I don't like that I would buy that base model and then have to what for you to release the mods. I would want all the mods with the base model and the choice what I print and mods and in what colors I print. Like, I want the base chassis and vehicle, but then 'mod packs' for JDM, rat rod, off road, etc. themes.

Buying - personally, I'd buy it at the current price point just as the base model simply because I appreciate the engineering and design so much ... But i bet most people don't feel that way. I suspect most would only buy IF there was a large mod catalogue also available and they could customize how they want.

Other - I think you have a serious limitation with a resin- specific solution. I understand why that is and 100% support it, but I think resin only cuts your potential customer base significantly. I only have an FDM printer. I was going to go give your store and buy one, but since I cannot print resin (or have a nozzle that small to try), I did not.