You are fighting the system because iM08 is limited when placing content. It is the whole 'Apple knows best' issue. Beyond your home Movies folder, it can also place content onto external drives at the top level in an 'iMovie Events' folder.
Also note that iM08 looks at those directories as a library. Placing other content in them manually isn't likely advisable.
You didn't mention 'another' editor before, but it might be possible to share the iMovie content with it. Maybe. I think this dangerous though because if either application alters the file, who knows what will happen the other application.
Unix links are pointers to real files or folders that appear as a file or folder when referenced from the system, such as the Finder. In Terminal do a; man ln.
To link a folder; ln -s <remoteRealFolder> <linkname>
A link is kind of like a Finder Alias. Don't try Finder aliases for this purpose though.
Lastly an internet search turn up this
trick which I think might require QuickTime Pro.