Interesting few posts, doesn't seem like there is an easy solution.
I agree with you. Solutions aren't obvious. I do think finishing the blast with a finals weekend before the hundred rather than having the hiatus seems a bit of a no brainer. Make it an early season competition - I don't think that would do it much harm. And the overseas players counties sign could be available for the whole competition in most cases.
Of course, that still leaves the big chunk of the season where the hundred must now take precedence because the ECB need it to be that way. My views on that don't really add anything as my skin in the game is hating it up front, so I hold my hands up to it. I think the 50 over competition probably will have to be pitched into the long grass and the calendar continues with two short formats maybe? The blast gives all the counties funding and the 50 over really doesn't now, especially as a 2nd XI competition because of the Hundred draft requirements. I like 50 over cricket, a lot, but I do sort of have to be realistic that it is the likely casualty of trying to make the summer calendar work.
I fervently wish the Hundred hadn't been created. But it has, and it won't be leaving the calendar. Therefore, the calendar has to be worked to make the best of the situation, both for the counties and the international teams. One thought is that the evening format and short timescale of the Hundred actually lends itself to the end of the season rather than the middle. It doesn't need the light in the early evenings in the same way as the four day game or 50 over could benefit. But September it is competing with football. All rather a muddle.
We now the fifty over is the poor relation, so perhaps that could be an early season affair, with games fitting around the early season of the county championship, and an early final at Lords say in late June, and then the late season is blast, hundred, and the conclusion of the county championship?
Dan has it right though - there is a fairly short weather window, and now the ECB are trying to fit four competitions in a space where there were previously three.