Kinda been wondering about this for awhile. Seems like it would work well.

12.19-in (310mm) x 32mm front rotors, Superlite-sized calipers from AP or StopTech. Inexpensive consumables. Essex Parts has a similar system available for the FR-S. Rotor selection is whatever you want, from really lightweight straight-vane stuff at $40/rotor to 60-vane, HD stuff at around $130-170 at the top end. Pads are standard circle-track pads, so available in pretty much any friction you want for really cheep.

12.19 310x20.6mm rear rotors. Might be able to get away with using the later JDM rear calipers that are meant to run on a 314x20mm rotor. This would be lighter and the replacement rotors cheaper.

This combo should fit under 16-in wheels. Don't know if there's enough clearance under stock FD wheels to fit it, since the front rotor would be 10mm thicker than stock.

Just kinda throwing this out there. This isn't a feeler for any brake project, just something I thought of awhile back. Thought other people might like to think about it, too.