In november 2010 I've posted a proposal about a 5170 with white metal case, but I totally agree with your suggestion: a blue dial would be just gorgeous.
First version (november 2010, inspired to an old PP chrono).

Second version (same vintage style, with pulsometric scale; all the writings are printed in white, the hour/minute/small seconds hands are in white gold, the chrono hands are white painted).

Third version (did you had in mind something like that? if not, could you write me a detailed specification? personally, I find that this design has a certain déjà vu and that it isn't recognizable as a true modern Patek Philippe, even if I have pictures of an old PP reference having a similar layout).

Fourth version (as above, but with enlarged subdials and without number 3-4-8-9).

Good night!