Padma, all of these solutions reduce the breadth of view of each AD, which in turn limits the opportunity for there to be someone in whose head a lot of siloed threads of work are known. This is why I am arguing that this isn't the right approach to the problem. When I was AD (and I realize that not everybody considered this a feature) I really felt like if I just relied on directorate reviews without reading the documents myself, I wasn't going to have that overview, and that cross-pollination of ideas would suffer as a result.
I would not say that this is an impossible problem to solve, but what you've described will not solve it. In order to solve it, we'd need for the directorate reviews to concisely summarize what each document does, with enough detail that the AD who's the recipient of the review has roughly the same mental picture they would have had if they'd read the document in detail; just with less detail. I think this would be great, but unfortunately this relies on the directorate reviews being of generally _much_ higher quality than they are now. And I say this having been the recipient of some very good directorate reviews recently: these reviews would not have served the purpose I'm describing.
So if the right answer to this is to make AD a 10% position, we have to figure out how to significantly increase the quality of even already-good directorate reviews. I'm not saying that's impossible, but we'd have to figure out how it can be possible.