intelligent Customer 1 / 2 careful drafting
Hmmm!
My last aircraft programme, C2 declared they would not support the programme in any way, so it was just a DIY job from start to finish. My last Army programme, both C1/2 went AWOL, but the end users more than compensated, immediately accepting that the Yeoman of Signals knew what he was talking about, so no need to get involved above junior NCO. Completely ignored DEC's original KURs and delivered exactly what YoS wanted, much to the Management Board's annoyance. In fact, what you just said JTO!
In practice, the best way to deal with a nonsensical URD was for the project manager to prepare a "clarification paper", have C1 sign it and stick it in the back of the URD as an Annex. This avoided resubmission and many buoys. This became ever more difficult as PMs were no longer required to know this stuff, partly because aforesaid HQ sections had closed and no-one had the experience. I recall one job in 2002-3 when my spec called for systems integration (and, hence, functional safety). The sole purpose of the programme was to reduce battlefield casualties. A senior officer called a halt and let a 6 month contract on a consultant, asking for a report telling him what "systems integration" was in the first place. The problem was (is), MoD's rules rather assume this knowledge, merely mandating the procedures for implementation. A solution emerges....