I've always tried to use Toyota or Denso whenever possible. However, when it comes to rotors there are better options. On more than one occasion I've had brand new OEM rotors come to me out of spec. One set was so bad I had to turn them so they'd fit.
I don’t see our year Sienna on their website, but planning on calling.
One thing I noticed from their pictures none seem to have the thumb rest at the 4 and 8 o’clock positions that our Sienna does.
Our's doesn't have the bed slats, but 3 pieces of the very nice laminated plywood. However, I'd like to add some aluminum framing similar to what you're doing & include some hinges or struts to increase rigidity.