I often would like to be able to remove bulky attachments from old e-mail, while keeping the text of the message for record purposes. this is for example implemented in thunderbird, and I find it a very useful feature. It shouldn't be too difficult to implement, at http://people.debian.org.tw/~chihchun/2006/10/23/remove-attachments-plugin-for-evolution-001/
they claim they implemented it as a plugin with less than 100 lines of C code.
I haven't tryied that plugin, as the install procedure requires a full evolution source tree, and is far beyond my capabilities.
I hope somebody will find time to add this feature. thank you