Do you think this will get you help in any way?
I’ve been a professional game tools programmer for 15 years, but given that you didn’t actually answer my questions, and started calling me names, I don’t know how to help.
The best way that your meshes will work for customers using the Epic rig and the Epic animations, in a world where things other than your character only exists, will be to detach the objects that use additional bones, and provide two sets of meshes and animations: One set that targets specifically the humanoid rig, and one that targets the “extra” bits you add. Users can then drive your extra bits using the animations you provide, and drive the base character using mannequin animations re-targeted to your rig.
There are other solutions, too, but you haven’t actually spelled out what the problem is you’re trying to solve, so it’s hard to say more. WHY do you think more random bones in the Unreal rig are needed? What is your input data? (Mesh, Rig, Animations) What is your output data? (Mesh, Rig, Animations) What is your tool path? How do you expect paying customers on the marketplace to use your final assets in game, in combination with other Epic assets?
Your attitude to how to provide working meshes and animations to actual customers seems to not be a good match for a well functioning technical marketplace.
Creating good game art is 5% inspiration and 95% transpiration, and based on your answers, you don’t seem to want to do the hard work necessary.