Duck,
In the past two years, our squadron has had 3 people attempt early separation by the same means you're asking about, twice passed over. One of them wrote his Do Not Promote letter to the board after his PRF was filled out, signed, and he had gotten a DP. He was not passed over, unsurprisingly.
The other two made their intentions known to their leadership. One of them, after telling the Sq/CC about their plan to write a letter, met with the Wg/CC as well to argue for a P, and got it. That person's argument was somewhat compelling, much like yours sounds to be. They then wrote their own PRF and followed up with the exec to ensure it wasn't fixed "too strongly." The only push back here was that the Sq/CC argued that sending off a PRF that was "too weak" would reflect poorly on the squadron. So the PRF ended up being neither really weak nor the best it could be, but with the coveted P.
The other person rolled the dice and only told the Sq/CC about the letter and hoped for the best regarding a P or DP. They also got a P, and were passed over. That person's PRF was weak to begin with though, due to making their intentions and motivations (or lack thereof) known years earlier, so the P followed from that.
Not sure if this helps, but it's three more data points.