Unfortunately, I have no time at the moment to write a detail comment to this post. But you may want to check out scipost.org that is a common platform used in physics and that accommodate most key features mentioned. Its clear advantage is that it is built on an existing infrastructure already well accepted by researchers, the arxiv.
I will try to find some time to answer more verbosely later, but I cannot promise. My life is so busy since 2 years...
PS: thanks @agmoore for the mention.