My idea would replace the following w/ one click (on the tool bar or
context menu):
Open email
Select desired attachments (displayed at the bottom of email)
Right-Click attachment(s)
Select Remove
Close email

Have you tried selecting the attachment in an open message and right
clicking on it? You should have an option called Remove. In Outlook 2007,
as the first attachment fills the preview, hold shift and press the arrow
key to select the rest of the attachments. I don't have older versions to
test, but I'm pretty sure you can select and delete (remove) multiple
attachments from a message (but not remove attachments from multiple
messages). You'll need save then close (or save when asked, after you hit
close) in order for the changes to be saved.