Hi Miguel,
Below my comments on some of your points:
B) The bio is user private data and I don't think it's convenient to allow anyone else but the user to edit it.
C) Showing content on a mouseover event has accessibility issues (e.g.: keyboard-only users, visually impaired users). On the other hand, if you decide to use Ajax for its implementation, be sure to do it in an accessible way. Finally, as you mentioned, if a class has hundreds of students, it may take a while to load the page in some cases.
D) Adding icons to make .LRN UI more friendly has been discussed for a long time now. IMO, icons should be part of a theme to be applied on the whole site and not on a per-page basis (for sake of uniformity and usability). There's ongoing work for managing themes for OpenACS that eventually will support collection of icons.
