Do that many people maintain domains on multiple registrars? Seems to me like the kind of person for whom this is a problem would have already simplified their own life by picking a single registrar.
If this type of service minimizes "their cut" to the bare minimum, and made it very transparent who it was coming from so i could price check, i would likely use this service because they're bound to have more TLDs (due to aggregation) than typical registrars.
Unfortunately, currently i feel like i'd just be paying a significant premium for something i already find too expensive. And if this isn't true, i see no information to indicate otherwise (at a quick glance, at least).
Nuage has a very simple UI (much easier to use compared to gandi, imo)