Frankly, I'd be happy to incorporate it into my library configzen.
ION, MsgPack and ConfigObj backends are not loading because of backwards incompatibility with anyconfig.
If you are planning to drop support on this one, please let me know, I'll then include this project in my library, continue its development, transfer issues from this issue tracker and fix any new bugs. Otherwise I'll be uploading fixes here, as PRs, using anyconfig as a standalone package.
I just want to make sure that those would ever be reviewed. Last commit here was quite a long time ago.
Thanks!