I've considered it, but as long as Spanish cedar is still available, I think it just has too many advantages to bother with redwood.
I was thinking of doing a laminated neck with rosewood center strip for strength, but then noticed it might be tricky to carve rosewood and redwood at the same time, so then I thought maybe douglas fir strip, or embedded carbon fiber bar.
You'll need to reinforce the headstock some whichaway to prevent splits. Either scarf joint with handstop/volute, or backstrap with rat tail.
Also, make sure the heel has plenty of meat so it doesn't split either.
Since I don't like dented up necks, I was thinking I'd give it a French polish to burnish and harden the surface a bit, and then spray lacquer for a protective shell. But I'm not a big fan of lacquered necks either
Another reason I decided against it on my current build, is that I will be using friction pegs for tuning. Redwood might be too soft to grip them, plus danger of splitting if they're jammed in too hard. Could put in bushings of some other wood, but that's just another unnecessary step when there's a hunk of Spanish cedar sitting around.