I just used a standard resume and changed "resume" to "freelance portfolio" and made clear that all entries were freelance/remote work. I didn't provide any contact info and as said I wasn't asked to provide anything else. I think your idea sounds excellent and will be accepted without issue.
I have just applied with a "freelance portfolio" which is basically just a resume with my current and former projects and I will let you know if they accept this or request further info.
So a stupid question: With this you can leave and enter as many times as you like (and will always get 180 days), correct? Like I would be spending significant time in Thailand for those 5 years but fly back to Germany to visit my family 2-3x per year, this would not be an issue at all?
I also believe a "Freelance portfolio" would basically just be a resume on an, "official looking template", as you say. At least that's what I will try it with.