I think adding the ability to mod the game would extend its life and allow the community to add lots of new content to it. It would also make the forums a lot busier with people discussing sounds, models, weapons, maps, and skins.
W4:M gives us the ability to tweak some features, but I bet lots of people would like more. Just look at Quake, Unreal and Half-Life. They're old games, but people continue playing them due to the many mods, maps and other stuff that have been created for them.
Just my 2 cents.:)

Stay tuned. There's rumours that a Level Editor will be released by Team17.

it is possible to moddify maps, sounds, and skins allready. unfortunately, very few tools exist to help you with that, so a lot of it has to be done either by hand with a hex editor or by writing your own tools.

I wonder how this "Level Editor" will be, because modified maps don't work online. :-/ Maybe it will come with a patch, or something like that (or maybe it's a stupid joke...)

I wonder how this "Level Editor" will be, because modified maps don't work online. :-/ Maybe it will come with a patch, or something like that (or maybe it's a stupid joke...)

The editor for WWP came with a patch. Or maybe it's a stupid joke. At this early stage, we just don't know.