Keep in mind I mostly make characters and simple props, so take what I say more as generalities than cold, hard facts.
My understanding is that any clothing set needs to be modeled against the base figure first and fits then added for any custom character/shape you might have created and some support for the more popular shapes (Michael 8, etc.). I do not know how many Daz3d core figure shapes they expect supported and what is fine to leave to autofit, but that would be something they would tell you after you receive the “go ahead”.
My suggestion would be to test the waters with Renderosity first. They are a little less rigid in their acceptance process and it will give you an idea if what you think is amazingly creative and a “must have” product is received the same way by the customer base. I started there myself and because, back in the day, I mostly made Caucasian, pretty females, I did well.
My first submission to Daz3d was a single, artistic render of a male figure. They responded within a day or two with suggestions and told me to go ahead and submit it. At that time, however, I was a top seller at Renderosity and I had also included a link to my store there. So when you do decide to approach Daz3d, show them your very best renders. Don’t feel limited to technical ones showing the product details, but definitely include eye-catching, artistic renders. If you(please don’t take this the wrong way; I don’t know your render work) feel your renders don’t “pop”, don’t hesitate to hire a promo artist. My understanding is some will do the work for a copy of the final product, some want a flat fee, etc.
Also, when you import your modeled clothing, using the Transfer Utility is the most common way, as I understand it, to rig the clothing for the figure you created it for. However, that usually isn’t the end of your work. You then need to pose a base figure wearing your new clothes in semi- extreme positions and then create partial Joint Control Morphs to fix the distortions you find. Obviously, the skimpier the clothing, the less of these issues occur.
This product is great for posing the figure for you to find those problem areas.
It also includes on the product page, a helpful video about creating these morphs and moving the clothing between Daz Studio and an external modeling program.
And the morphs in this bundle(or their separate components) can be used as a Merchant Resource in clothing:
Clearly, this is just scratching the surface. There are YouTube videos out there by Daz3d that walk through some of the processes, but I’m only familiar with the ones related to character creation.