Please provide examples of what translation or hack wouldn't need a readme? Every patch needs to at least provide information on what ROM it's for at the very least. In addition, most likely an explanation for what the patch even is.
I'm not DMM, but I'd rather see a submission not mentioning those things in the description rejected than one not including a readme. I've always considered the readme field to be redundant when a well-written description should be available for every entry on the site. Let's take a look at the descriptions for hacks with "No Readme" on the maintenance page:http://www.romhacking.net/hacks/618/http://www.romhacking.net/hacks/600/http://www.romhacking.net/hacks/615/http://www.romhacking.net/hacks/353/http://www.romhacking.net/hacks/604/http://www.romhacking.net/hacks/613/
Of those, only the last one is truly bad. Maybe 353 too, but you know the history behind that one. 618 and 600 are shining examples of the description field being used to its full potential: they tell you exactly what the patch does, which ROM to apply it to, and in the case of the first, even what you need to apply it. I hardly see the need for a readme in either of those cases. (I also submitted both of them myself, and wouldn't feel right writing a readme for something that wasn't my own, nor would I want to see them rejected over something so trivial.) 615 is a hack of a GBA game; it could probably mention which region ROM it's based on, but you don't have any wacky header issues to deal with there. Same with 604; it mentions an unheadered ROM, but not the region.
Really, the solution isn't requiring a readme. It's requiring well-written descriptions, and possibly adding a region and optional header field to the submission forms and file pages.