timroes, do you mean something similar to what doodle does? See e.g. http://www.doodle.com/s3cw2n42ysy8uhhy
<= There you have a certain "accordion-like image" when some entries are skipped. When you click on it, it opens the table in full width. Even the whole page gets wider. So, that's very close to what you described. Although, I don't like changing the whole page layout for that.
turnermm, (too wide) tables should behave the same everywhere (so, including tables created by plugins and in admin panels).
Toggling the sidebar on and off is not a real solution, as this would only give you a few pixels more. So, it's a solution for only those tables which are a little bit wider, but not for those which are much wider. Those very wide tables would still need a solution...