A complicated issue, but at least as a quick reaction, I would see more cons -- and also risks in terms of image -- than pros should Patek go down this route.
Not to mention that a new SS sports model in the $18-20k range would instantaneously end up like the 5711 or the 5167 on the secondary market...unless Patek releases it in generous quantities, which will never happen.
An elegant step that partly goes in the direction you mention is the new 5212, at least in terms of appealing to a younger but sophisticated base. However, they sensibly remained on a price ($30k) and distribution levels that preserve some exclusivity. If I have to guess, you'll hardly see more (i.e., less) than this from Patek in the near future ;-) Cheers.