Why not leave it up to the certifier whether the map is legible or not? We give the certifiers the responsibility to make a lot of other judgements about the quality of the maps that are equally important.
We have a large variability in the quality of our maps, and 150dpi vs. 300dpi is close to the bottom of the list of things that separate a good map from a not so good map. If a map is legible the dpi is irrelevant.
I understand that the format is what it is for now, and we should work to meet it and figure out how we can make it easier for others to meet. But in exchange for that good soldier behavior, we should be promised that the plan is to eventually change the arbitrary and outdated requirements (only talking about file format) that are currently in place.