We’ve only started planting cabbage since the fall, so I’ll be brief and defer to the experienced cabbage growers along us.
Both of those ideas sound great to me! The very small amount of cabbage we fall-sowed either didn’t come up or got ate, but I’ve little doubt the notion itself is sound. A number of cabbages are very hardy.
I had better luck with a grocery store savoy. It is still hanging in there, unmulched, after a bitterly cold December.
Whatever makes the most sense for you of late summer, fall, or even winter planted cabbage makes an awful lot of sense to me. On a tangential note, I believe chicories are often summer or fall planted because the frost-induced change in flavor is desirable to many growers.