Very interesting. Thanks for the pictures. I think I see where you are going here.
I think the final blingness coefficient might be assisted by upgrading from the Simplex Criterium RD with plastic to the more modern Simplex SLJ. A Simplex 6600 RD paired with the Modern Retrofriction downtube FD would look nice (or did you say single speed?).

I also see you have the new Brooks seat but what about the older Ideale with a nicely polished, shiny aluminum rail structure? The leather might be old and possibly need replacing but a 90R with a black seat along with black cork/leather handlebar tape might play off the bling nicely. Also there are some good leather seat workers here who could totally replace the leather if you could not find one with good enough leather.