Well, here's a simple proof of concept. It has a working profile and edit tab, and columns in the profile tab can be controlled with parameters (in the My Events tab setting). It's been tested so far with Joomla 1.0.4/clone() fixed Events Calendar 1.2 and the unofficial 1.2.1 (Geraint's hack) found here:
forum.joomla.org/index.php/topic,6217.0.html
Although it doesn't add table fields and installs/uninstalls okay, definitely DON'T use this plugin on a production site just yet. Still need to fit in time offsets and a basic ACL check, and some of the formatting's still hard-coded.
If you try it out, let me know with the version of Events and Joomla!/Mambo you're using if you encounter a bug. It'd be very helpful. Thanks!
Attachment eventstab_0_1_alpha.zip not found