Here is a potential way to push more white Doffs into Fleet Projects.
Find and purchase cheap Green/blue Doffs on the Exchange, or use unwanted green/blue Doffs from your crew.
Go to the personnel Officer and Exchange Duty Officers. This costs zero dilithium and creates 3 Doffs of next lower rank. You can do this an unlimited amount of times.
Mail the extra and currently unneeded Doffs to yourself for later use (see this post).
This works best with KDF Doffs, as you can execute any unwanted civilians.