DMC, I would also like to add that along with gentle mixing, low water/dough temps, a highly hydrated dough (as mentioned before) and a high % of oil does indeed lengthen the knead time to develop gluten even if one is working with a HG flour.
What I find interesting is that you mentioned you don't like to use HG flour b/c it gives you a dense/chewy crumb. I on the other hand also do not favor dense or chewy crumbs and am VERY sensitive to it. But yet my favorite flour so far is a bromated HG flour. With a high hydration ratio, and with a gentle and minimal knead time (4 min of mixing ingredients and another 6-8min of gentle and slow kneading) I get the lightest, airiest, fluffiest crumbs. I've posted pictures of this. DMC, I know you already said that you knead with cold water and gentle kneading but I'm curious to know if you've tried this with a short knead time on a HG flour and still get a dense or chewy crumb?
I don't know for sure, but it makes sense to me that HG flours will give an a better/stronger crumb structure to support loftier crumbs (read light and airy) if done right. If not then it can definitely give a dense crumb which I have experience with ATs flour.