Mark, I'm somewhat uncomfortable with your proposal also.  It changes
what the parser will accept and the potential benefits are almost nil. 
Also, putting NaNs and Infs in complex numbers is probably not something
that should be pursued.  I see no utility in pairs like (NaN, 3.0) or
(-2.0, Inf).  The whole request is use case challenged.  AFAICT, the
current implementation suffice for real cases and there is no compelling
need to rearrange and redesign this code.