If no delay is allowed, then why can vehicles get up to the ISS if they have any delays? That's an equally complex orbital rendezvous, and yet we achieve it all the time without difficulty (OK, we used to - however the problems have nothing to do with launching the vehicle to the right orbit). With the new vehicle's elimination of the need for massive cryogenic storage, it should eliminate many problems, and the lack of a parallel staging system eliminates even more. I fail to see what your issue is.