Sempre Pro with a pannier rack?

Carbon fiber tubes are very strong against torsion and bending forces. They are very weak against impact and compression. Carbon fiber frames are optimized to resist the forces of the weight of the rider, the torsion and bending of pedaling, cornering, and harsh roads. To a lesser extent they'll take the impact of small flying rocks, the sort kicked up by wheels. Tubes are strongest at junctures--head, seat, bottom bracket, and dropouts. I presume you would be mounting the rack using P-clamps on the seat stays and/or a mono-stay adapter on the carbon seat post, introducing bending and crushing forces where they were not anticipated in the design.

The blather in the competitive cyclist website about the relative strength of the Sempre Pro is their interpretation of Bianchi's marketing of nanotechnology. Basically, as carbon frames got lighter they used more carbon fiber and less resin, the stuff that bonds it all together. Most carbon frame failure has been the result of resin failure, so bike companies use and tout whatever they're doing to improve the integrity of the resin or use it more effectively. Bianchi's calling card is "nanotechnology," nano-particles that fill micro-gaps in the resin.

So, beyond using an alloy seat post and attaching a seat post rack to it, I would not mount a rack to a Bianchi Sempre Pro or any other bicycle with a lightweight frame (carbon, aluminum, titanium, or steel) that does not have mounts and is not designed for attaching a rack.