I work for a large university (part-time) and with their knowledge have additional smaller clients for whom I also write (non-competing) proposals. As a grant writer, I have always specified in writing what I would accomplish for my clients. I also keep all of my e-mail correspondence that includes the questions I've asked about specific tasks, outcomes, objectives and goals that I've written into the grant along with their approval of the final version.
No agency accepts a grant proposal signed by the grant writer, it gets signed by a Dean, Provost, Principal Investigator, CEO, or Director or some combination thereof for the very reason you described in your posting. As a grant writer, your job is to take your agency or institution's vision & put it on paper in such a way as to inspire a funder to give them funding. You're not there to implement the program.
Find another agency who will appreciate your time and effort and will use the money you obtain for them responsibly.