I can fit my jack, torque wrench, jack stands, and small toolkit in the trunk.
The reason for this instead of a full-blown trailer is that I have nowhere to stow one. Now that one in the picture doesn't look too sturdy. I'd probably go with something more rigid instead. One of my fellow autocrossers looked at my car this today and said that he could fab up something quite simple that would work just fine for what I need.
And Uranium...I ran my A6s this weekend after a really heavy rain under super-damp conditions...even some 1 inch puddles!!! I did have to give up just a little bit, but they still stuck pretty well.