Workaround for Document Library Change Request #4
I think I've might found a workaround for my 4th issue. The problem was that customers wanted to store several attachements in a mail into a Document Library located on a WSS site. Of course, the solution was right in front of my nose the whole time.
We're already integrating with Exchange through Outlook Web Access by simply displaying a public folder dedicated to the site (which in turn is dedicated to a case or project) in a Page Viewer Webpart.
Then it struck me. Why don't we just create a new document library on the site and mail-enable it? When you've got files related to the site (case or project) attached to a mail, you usually want to store the mail aswell, so you just click "Move to folder", and (with the public folder as a favorite in Outlook) it pops right up. Then Sharepoint detects the mail after a while and extracts the attachements into the "Email Attachements" Document Library on the site.
This still doesn't solve the ad-hoc need to store attachements any document library on any site, but it can be used to solve the cases where users most often wants to stuff an attachement into Sharepoint.