Yes you can although i guess a duvet stlye might stop the turnouts wicking/sweat evaporation techniques working?
Not sure though , never done it myself.
I layer mine with turnout rugs as I don't bother with stable rugs these days as they keep their turnouts on in the stable! And if you use turnout rugs to layer, then if the one underneath slips out a bit, then it's still waterproof.
I put a medium weight turnout one with a lightweight over the top. If it's been raining, you can take the lightweight one off and dry it more quickly than the heavier one, but you could do it the other way around.
Last winter, when it was deathly cold, I had a heavy weight with neck cover under a medium weight wug on a fully clipped horse. Worked very well indeed.
Really, you could get away with one medium weight with neck cover/full neck and one lightweight all year round, just put them both on when it's very cold.
my boy works through the various weights of t/o, then has a fleece underneath, then 2 fleeces, then the stable rugs. as previously mentioned, layering t/o's works well as they don't soak up rain!