Good post.
The domestic schedule for next year is still being finalised, however when the international fixtures were released yesterday they did say that the T20 finals day will be on July 16th. That suggests that they may be going back to the format that you talk about, where T20s are mostly kept to evenings and weekends with Championship being played around it. The Hundred will almost certainly be later in the summer as the women are involved in the Commonwealth Games in early August and they won't want to split it from the men's tournament. The problem is that they have to schedule something opposite it, otherwise you'll have dozens of county players who aren't involved in it sat doing nothing at the height of summer, which means the 50-over comp will probably be played at the same time again.
Root has already said Buttler and Moeen will play, Leach will only be included if they go for a second spinner which I'd imagine is highly unlikely given that he appears to not trust any of them sufficiently. Wood will come in for someone, who that is probably depends on how fresh Anderson and Robinson are.