Finally, I got the crumb I've been looking for, and it came about by accident.
To enlarge the crumb, I've been gradually reducing the kneading time, lowering the flour strength and increasing the hydration of my baguette doughs. Finally, I got it right on New Year's Eve, when we were having some friends over and decided that crostini would be on the menu. My wife and I were both very busy that day and I was in a rush to get the bread done, since one of our ovens went on the fritz the day before (naturally!) and so we only had one oven to work with and lots of baking.
To make a long story even longer, I mixed the dough (Giusto's Artisan Flour, 75% hydration, 2% salt, 1% IDY) in my KA and worked it under the paddle for about a minute, when the dough started coming together and the gluten clearly was forming. Without thinking, I put it onto my kneading board, and only when it was there did i realize that I'd intended to work it under the dough hook for another couple of minutes. "Oh, well," I thought, "No time like New Year's Eve for an experiment." So I let the dough sit on the board and gave it four stretch-and-folds about 20-25 minutes apart. The dough came up beautifully.
Handling it very gently, I scaled it to 225 g/8oz and let it rest for another 20 minutes or so before rolling it out and arranging the six loaves en couche for about 75 minutes of proofing. Oven preheated t0 500F/260C. I steamed the oven, slashed and loaded the loaves, then steamed again at 3 minutes, reducing the temp at that time to 450F/230C. Baked for about 10 minutes longer and got terrific oven spring, as the photo shows. What the photo doesn't do justice to is the gorgeous yellow color of the crumb.
All in all, a very satisfying bake.
Next batch will be at 80% hydration, and I'll also see how other flours (i.e., Sir Galahad, Harvest King, La Parisienne) behave under these same conditions. Will keep you all posted.