Its not that they wouldnt be respectfull, its that they lack the skills/expirence.
When Metroid was brought 3D, if it failed theres no real lose, as the series hadnt done anything for ages.
Zelda has -a lot- more riding on it.
Also, I dont see many skills from Metroid that carry over into Zelda. Sure, the games have a similiar progression structure. But Metroid really has nothing like the enviromental interaction with items that Zelda does. And for me that -is- Zelda. Getting items that do different things not related to killing stuff. Corruption had this a bit with the welding (which was great), but not much else.
I also hesistate given them the franchise thats 3rd person and a lot of NCPs.....different art skills required for that.
No, I think Retro should branch out, but to something that fits their skills more. (Not to mention existing engine assets).
Retro making a "Giest" game would be brillent, no?
I could also..strangly...see them doing a good Lugia's Mansion for the Wii. Much bigger, more first person based, but still the same mechcanics could work well.
Regarding Retro's skills in incredibly enviroment design, well, thats applicable to nearly any game. Their enviroments would look equaly cool in FZero, for example
As for Zelda, Id keep the present team working on it, but Id love for Nintendo to colaborate with Capcom.
Not only did Capcom make MinishCap...which was fantastic....but they also made Zack and Wiki, which has some of the best puzzles Ive seen in any game.
(And also, a perfect example of puzzles solvable by "just whats lieing around"...an approach Nintendo should take more).