I have been thinking about the file format to upload mesh models that might ultimately be settled upon and just wanted to throw in my opinion, for what it is worth. I understand why .fbx was used as the initial format, for Autodesk is the industry standard for professional 3D artists.
I think it depends on who you see as your target content creators. Are you thinking that the majority will be professionals, or perhaps that may even be seen as the ideal. For industry professionals, it is expected that they would be using Autodesk products.
As a hobbyist and content creator on a more modest level, I would not be willing to pay the cost to buy Autodesk or Maya LT, priced at over $3,000 US. The monthly subscription cost of $50 US a month for Maya LT is an improvement over that, but still more than many hobbyists would like to pay, especially when there is Blender that will do the job for nothing, or the more modestly priced Modo and ZBrush.
If your potential target is to include as many content creators as possible, could I recommend perhaps adopting the .obj format? Just about every 3D program out there will export to .obj. It seems to be the common format that all the programs can read.
I don’t know if some formats have more advantages over others in terms of data that can be carried in that format. Perhaps those who are more knowledgeable than I can comment.