“You'll note that there's a common theme running through them: the end state for the opponent is ‘out of options’”
“Luckily, a combo like Cifka's Second Breakfast depends heavily on being unknown, since there are entire classes of cards that interact with it in extremely powerful ways once the proverbial cat is out of the proverbial bag”
“This brings us to the detain mechanic”
Wow you guys really do not see the forest for the trees – WU does not even need or care about detain. It already has the win ticket without it. Interaction against WU is already screwed with Geist of Saint Traft, Azorius Charm, Supreme Verdict, and Jace nobody can play anything but WU with wining chances. Recursive WU is rampant, every other color combo is irrelevant at this point…even Selesnya gets stomped.
Seriously, you need to give the OTHER colors some MAJOR bullets in Gatecrash (perhaps give red/green some teeth). At my card shop all the non-WU players are greatly demoralized and some have already given into the WU.