HTV onto metal or carbon fiber

No clue about sublimation on carbon fiber. Sign vinyl looks perfectly fine and doesn't have a cheap look but looks very high end. More expensive sign vinyl will last ten years in the elements. Oracal states eight years on their page for 751 and up to ten for their 951. The cheap stuff can go three to five. Either will go even longer if you treat it with frog juice or something similar. With something like frog juice you could probably get normal paper to last a few years, though I'd never do that, just saying that the protective coating adds considerable durability and UV resistance.

https://www.signwarehouse.com/p/superfrog-7000-sunscreen-clear-frog-juice-12oz-spray-can-frog-juice

You might get htv to stick to those. I'd be leary of it. Adhesive vinyl would do better.

You can sublimate onto metal if you add a polyester coating. I doubt you can sublimate or use HTV on carbon fiber, the heat would probably melt and/or mess up the resin?

What about making a plot cut stencil from sign vinyl and painting/etching the material? Paint it and add a clear coat on top?