^The key is having strongly written characters and a good cast to carry the episodes. Also keep in mind that a lot of the substance of the book was expressed via internal monologue. It's one of the things the movie struggled with and any competent attempt to faithfully adapt the book would need to find a way to translate those inner thoughts and motivations into actions and words. And I do mean *translate*. Having characters simply spouting off what's on their mind or making massive exposition dumps would be a very bad idea.
That plus the need to gradually explain the setting to an audience mostly unfamiliar witht he books should make for plenty of opportunity for expansion.
As for it being the best approach: well, when you're talking about a TV show rather than a movie, or a mini-series it really needs to be viable for as long as possible. Straight up adapting one book per season just won't work for Dune because the second and third books are significantly shorter, so you'd have to do what the mini-series did and shove them together.
That give you two 10-15 episode seasons of television and you're already into giant worm man territory and 95% of you cast has been killed off. Any attempt at tackling GEoD and the later novels is going to feel like a soft-reboot with an all-new cast save Duncan, which is going to be a hard sell under the best of conditions. After only two seasons, it's pretty much ratings suicide.
P.S. I'm sorry, I still don't see any major "borrowing" going on. Everything you cited seems pretty superficial, most of which are as you said, fairly common tropes and the story structure is right out of 'Hero with a Thousand Faces'. Hell, that's kind of the point in Dune with the missionaria protectiva implanting the panoplia propheticus outsider/messiah myth as a safety net and psychological lever to move the masses.
Thrones on the other hand is using the trope totally without irony.