I'll add creating a web.config to the windows CLI client. That's easy enough for the mime-type.
The second part where StaticFile needs to be ordered higher was needed on my systems. Maybe because I've been using ASP.net MVC on them. I had to find and follow this: asp.net - extensionless image file not visible in IIS7.5 - Stack Overflow
It can be done in a web.config as well but it dumps out all of the handlers (there's like a hundred) to define a new sort order, which isn't a very good solution.
I just want this to be as painless as possible. Asking someone to go mess with their IIS config and potentially breaking things or creating security holes is not a good solution. Seems like a real pain when a small tweak to the ACME server would solve the problem.