Firstly, I want to say I really understand why you don't want AI in any of the final product, in any capacity.
With that said, we are quite a few people suffering from Aphantasia ( https://en.wikipedia.org/wiki/Aphantasia ), and AI has been invaluable for our ability to create art.
The way me and many others use it is as a replacement for that lack of mental images. None of the generated art is used in the final image, I don't even trace the generated image, but I do use it as a reference image up on the side when doing my drawings.

To give a practical example, if most artists think of a unicorn-centaur, they have a clear image in their head of what that would look like and can reference their own brains when making design decisions on the blank canvas. People with aphantasia don't get that, but asking Midjourney or Stable Diffusion to give us that will give our idea a visual representation to reference.

Would this still be considered "You must not have used AI at any stage, including creation of assets", or would I be OK to join?