Change the layer of `show background rectangle`

The backgrounds tikz library defines framed (a.k.a. show background rectangle) which draws a background rectangle.

Now, when we have a picture that involves different layers (say, a background and a main layer), we wouldd like the frame of the picture to be drawn on the deeper layer (background in our case), or even deeper. However, it seems that the frame is shown on the main layer.

This MWE contains a single node on the background layer in a framed picture. The background rectangle fills the main layer, and therefore the node is not visible anymore.

documentclass{article}

usepackage{tikz}
usetikzlibrary{backgrounds}

tikzset{background rectangle/.style={fill=blue!5}}
pgfdeclarelayer{background}
pgfsetlayers{background, main}

begin{document}

begin{tikzpicture}[framed]
    begin{pgfonlayer}{background}
    node {Hello world};
    end{pgfonlayer}
end{tikzpicture}
end{document}

---

Note: I know that I could reorder the layers to let the main at the bottom (like main, background, mymain), but if I can avoid to surround the important parts of the picture with a mymain layer, that would be better.

pgfdeclarelayer{background}%
pgfsetlayers{background,main}%

documentclass[border=5mm]{standalone}

usepackage{tikz}
usetikzlibrary{backgrounds}

tikzset{background rectangle/.style={fill=blue!25}}
pgfdeclarelayer{middle}
pgfsetlayers{background,middle, main}

begin{document}

begin{tikzpicture}[framed]
    node [fill=blue] {hello};
    begin{pgfonlayer}{middle}
    node {Hello world};
    end{pgfonlayer}
end{tikzpicture}
end{document}