Hi Stefan,
Hey guys,
I finally got around to writing a draft of the proposed plugin system.
You'll find this work in the 'io' branch at
http://github.com/stefanv/scikits.image
It's still a work in progress, but I welcome all comments. Example plugins are
http://github.com/stefanv/scikits.image/blob/io/scikits/image/io/matplotlib_plugin.py
http://github.com/stefanv/scikits.image/blob/io/scikits/image/io/pil_plugin.py