Is focus stacking an option for you? Seems to me that it should easier to merge several sharp, medium-DOF images into one than to make one unsharp image into a sharp one.
You know, I've use focus stacking with macro work it's a lot of fun, but with landscapes I think it's pretty much impossible. I really like Zyrene Stacker. I think it's far superior to Helicon Focus because it can perform different merging calculations that you can add to yuor existing stack of images and it has MUCH better editing. The one fundamental truth to know about focus stacking before you begin is "ALWAYS assume you'll be editing it later to work out the kinks." But, to me, that's reassuring. And, it also makes me edit very carefully only the very best image.
The one kink that is sometimes impossible to fix is when a near subject is so blurry that it obscures the distant subject that you're lens is sharply focused on! There's no way around that. So, now imagine a landscape with lots of prairie grasses and flowers in the foreground. There is definitely going to be some "blurry obscury" going on and probably all over the place! I'd have to do a test, but that's just the beginning of the challenge.
There's the problem with the slightest amount of wind changing the posltions of subject matter between shots. And, then there's the mere fact that taking two shots won't hack it. It'll probably end up being at least 3, just to allow opening up one stop
. So, it's pretty impractical, from what I can tell.