If were me, I'd go the vinyl wrap method.
Nowadays, the professionals that deal in graphic designs using vinyls for automotive (and RV, Marine) applications can create, produce or reproduce any type of image and the material grades being used are very good, long lasting.
Furthermore, IMO the benefits of using a vinyl wrap vs. painted on are multifold in that
- The quality of the wrap(s) can be so good it's hard to tell a difference between being painted on.
- The installation of such is not permanent, and can be removed easily.
- The materials used today are durable, UV resistant and last.
- In the event of becoming scratched, torn or otherwise messed up, the wrap (or even a small section of it) can be easily replicated and replaced.
- In terms of color distortion of the aluminum or its clear coat I do not suspect that will be anything near what may occur if painted directly onto the clear coat surface. And, Yes, some weathering with occur overtime (and typically due to UV prone fading) but that will be the case for either. Proper maintenance (waxing will help mitigate such).
Also noteworthy to consider, if designing a mural (i.e. similar to a Logo) it can be much smaller small and be proportionally enlarged during the process of producing the wrap to the desired size. You can still have your friend design the mural on paper and then see it transitioned to a larger size in the form of a wrap.
I also personally suspect you'll likely end spending less in the long run particularly should removal of it come into play. Removal of the wrap is easy, removal of paint on top of the clear coat not so.
"Finding the Roads that Await Us!"
Rick & Lydia Williams