Well, it's already "otherwise allowed" on every other band, so that won't work. I think it's a bad idea, that part anyway, unless and until they can show that a problem exists with wider bandwidth signals. I don't think they thought this through very well at all, a strict reading of that part of the ARRL proposal would outlaw DV on all HF frequencies, and outlaw digital SSTV as well. What happens if tomorrow someone develops a really good digital mode, but it takes 1 or 2 KHz for it to work well? Do we cram them in 5KHz on 40M? Since rules take so long to get modified, it is a "bad idea" to hamstring future development, especially if there is no real reason for doing so.