Carbon road wheels?

Problem with full carbon clinchers is if you flat explosively and are unable to stop quickly your v. expensive Enve rims will be at high risk of serious damage.

Seeing Dura Ace C50 CL rim spares being sold separately on Ebay would possibly lead me to ask a shop/wheel builder whether they could rustle something up with something like custom drilled Royce hubs

I wouldn't bother with that really. Get a set of these and some Mack/Goldtec/Royce track hubs and build up with CX Rays and Alloy nips.

Cost you fuck loads less than ENVE 65's or those DA rimmers.