We implemented a RFC-style process at a previous employer. It worked pretty well.
One thing that was particularly valuable was ensuring every proposal came with a "alternatives" section (called "competitors" in the NABC model). We also made sure that every proposal included "do nothing" as one of the alternatives, to provide an anchor for a discussion about what would happen if we simply didn't take on the problem at all (or stuck with whatever imperfect solution we were currently using).
One thing that was particularly valuable was ensuring every proposal came with a "alternatives" section (called "competitors" in the NABC model). We also made sure that every proposal included "do nothing" as one of the alternatives, to provide an anchor for a discussion about what would happen if we simply didn't take on the problem at all (or stuck with whatever imperfect solution we were currently using).