The "Prooflike" designation is more about reflectivity than the obvious (and beautiful) "black and white" appearance of this coin. PCGS has always been tough on Prooflike designations, and unless this coin has 4-5" of clear reflectivity I can see them refusing it.
With that said, Prooflike 1879-S's aren't very rare on the ground (the last PCGS 65PL at Heritage only went for $218 earlier this year), and a crack/resubmit might just do the trick. Not that I'd play that game.