I suppose it depends if it's wet or dry.
Dry you could get away with (as seen last Sunday) 24/27mm tubs and a double wrap of bar tape. Carbon rims are do-able as wet braking isn't an issue, and they're strong.
If it's wet then you're into cyclocross territory as mud clearance becomes an issue. Rabobank (I think) used modified cross bikes a few years ago. Close-clearance caliper brakes start to go out of the window in favour of cantilevers.
Plain, boring alloy box-section rims would be the only realistic option as the braking is more consistent, plus they'd be more forgiving on the cobbles when running lower tub pressures.
As well as dog fangs on the seat tube I've seen a few of the bikes with mechanic-made bits of metal attached to the front mech to keep the chain on the chainrings.
Only my observations, of course - I've never ridden Paris-Roubaix