Hmmm... I use mostly blender and can make many things if I am willing to put in the time (I mostly just like making characters), and I am only familiar with daz enough to shape and export characters. Depending on the requirements I may have the skills to work on your ring, but I am not familiar with how to get it into daz itself. Although, since I work with mostly character making, I don't have as much experience with hard ops (I believe that is the term for designing things like robotic suits and stuff, a good skill set to have if you want to make hard objects even as simple as rings). I can set up nice textures, but as for shaders I only can make shaders for blender, I have no experience with daz shading.
As for your story and need to have direct control, that is perfectly understandable and I wish you the best of luck. I have avoided spending money for more than a decade since I started 3D model work, but in order to work at a speed where I can keep my attention span at, I caved in a month or so ago and started to by daz assets. I use blender for touching up and improving what could be done in daz (in fact I have a few people who usually use blender for touching up characters, I guess it better in that regard). That may be something you will have to face in the future. If you want, I could give you the most basic list of assets needed to have the most customizability over characters while spending the least amount of money. This does not include hair or clothes since I find what I can make in blender supersedes what I can buy (I do not like how they do hair in daz).