.. but it's another thing to do a 180 below the tops.
Indeed .. especially when there is a much simpler option for CNS 15. Presuming that the valley escape is OK, technically - and this will depend on a multiplicity of considerations, my preference would be to schedule both, for pilot option. Clearly, the only sensible reason (at least, that I can come up with) for the valley is that it produces much higher RTOWs ... if it doesn't, why even contemplate the additional potential risks ?
.. with scant thought to the secondary risks of such a procedure in case of errors....
This is a concern with operations for which the ops eng support either has no operational experience or, alternatively, doesn't have a very close relationship with the flight ops organisation.
I can recall a few comments over the years by non-operational ops eng folk which raised my eyebrows ..
Indeed, well do I recall, as a then reasonably experienced ops engineer (and GA pilot), my early exposure to airline operations .. I distinctly recall an F27 takeoff from the north coast .. the end of the runway disappeared under the nose in a manner which quite caught my attention. As I gained experience on the line, my other life approach to ops eng progressively changed to become much more conservative.
As to whether the procedure under discussion might have been designed by a newchum or experienced engineer is not able to be divined from the procedure itself. However, one would hope that the organisational protocols involved appropriate checks and balances as part of the normal design QA approach to life.