Slots can be Sliding like in Google Sketchup(for animation) :)
or like this in C4D :)
http://traveaux.steph3d.net/FichiersForum/4D_Onglets.swf
So you can have any number of slots you want :)

But seems you have a little idea in your mind :)
So we are waiting the V 2 with a constant impatience :)