BB is trying to develop a minimal mark-up set.
Last time I checked BB was still trying to sell his idea that txt70 contains "all we need" to do automated markup. He sells this idea by pruning away everything which doesn't fit his idea. If BB or others are now acknowledging that this txt70 idea is a bad idea then I would agree that a standard set of markup for PG would be a "good idea." The next area of disagreement would presumably be how one should markup documents. The rest of the world, after many decades of debate, has converged on the idea that explicit opening and closing tags are the way to go, "convenience" in markup being discarded in exchange for techniques that are robust and which can be well-automated. Which then brings us to some flavor of an XML markup scheme. What remains then is reaching agreement on what the "useful" set of tags should be. Suggest one could start by looking at the DP set of tags.