In what jurisdictions would that be interpreted as copyright reassignment? I can see how you might argue that "re-assign copyright to myself" is WTF you want to do, but the onus is on the creator to assign copyright to you.
> There's nothing to stop me from taking your code, re-licensing it under say a proprietary license, then suing the original creator.
Suing them for what? There's nothing to prevent you from suing pretty much anyone, for any reason, including any of the other licenses. Second of all, if you're saying there's nothing preventing your suit from being successful, I still don't understand on what grounds. It doesn't matter what licence you've relicensed under if the original author holds copyright.
> There's nothing that stops me from taking your project's branding/symbol/graphics/name and claiming it as my own and then suing you.
You could do this no matter what the license. What about the WTFPL would make your lawsuit any more successful than any other licence?
> There's nothing that stops me from taking your work and then not providing attribution back to the original creator.
This is fully within the intent of the WTFPL.
> By default there is nothing that absolves the license holder from warranty nor implied fitness for use.
You have a good point that this is something many people would want. Do you know in which jurisdictions this is actually needed? I wasn't able to find any sources for this.
> Has it been challenged before in a legal sense? Has a lawyer reviewed it?
Excellent points.