Re: Lynch's Dune was good, lots of people agree
It's not a case of switching it on though. As the "God of Biomechanics" explained to Roy Batty "the flame that burns twice as bright lasts half as long". Replicants aren't robots, they're gene-tweaked humans who basically burn out their bodies within 4 years. The entire futility behind Batty's doomed crusade to live longer is that he just can't be given an extended lifespan. In the end he accepts that.
Also, Gaff mentions it's too bad Rachel won't live. She was Nexus-5 (probably same as Deckard as neither of them knew what they were) and she clearly had the same lifespan issues so there's no reason to think he wouldn't also.
If they change that for the sequel (and it looks like they've either done that or ignored the whole thing about Deckard being a replicant) then they've fucked it before the opening credits have rolled.
Personally, I don't think Dune will work as a film. For some reason I don't trust Hollywood to be able to deal with pretty much any aspect of the book without fucking it up completely. Can you see them advertising a film with a protagonist called Mua'dib leading a group of fanatical warriors in an almost-accidental jihad against the entire rest of the human universe? May as well call it "Dances with Sandworms".
Oh, and if Frank Herbet's son is involved in any way whatsoever then I'd expect it to be a complete and utter pile of shit that contradicts itself every other scene.