Fixie styled Tandem?

While on the subject of tandems, why are the cranksets always installed the same way like in Fig. 1? I'd think that installing them at a 90 degree angle would help overcome the dead spot (Fig. 2).

People have experimented with different phasing http://en.wikipedia.org/wiki/Tandem_bicycle#Crank_phase but the conventional 0° phasing is the only one which really allows out of the saddle efforts.