You have gone through a complete description of all the features that Mongrel2 has right now, but not all the features it will have. I tend to write small software that does exactly what it needs to do, and Mongrel2 is no different. What you see here are the majority of the things you need to do right now, and we’ll be slowly adding things people need.
If you’d like to help, then join the mongrel2@librelist.com mailing list and then read the Contributor Instructions.
Thanks,
Zed