How to scale a Tikz pic, when it should be positioned absolutely

Question

I have prepared a MWE, where I have tried different approaches, how a tikz pic can be scaled AND positioned absolute:

 \documentclass{standalone}
\usepackage{lmodern}
\RequirePackage{tikz}
\RequirePackage{pgfplots}
\pgfplotsset{compat=1.11}
\usetikzlibrary{positioning,backgrounds,symbols,shapes,shapes.arrows,arrows,shadows,fit,calc,matrix,decorations.text,arrows.meta,shadows.blur,shapes.symbols,automata,fpu,intersections,fadings,shadings}

\tikzset{
Test/.pic = {
    \draw (0, 0) arc[start angle=180, end angle=0, x radius=5cm, y radius=2.5cm] 
            -- ++ (0, 2cm) arc[start angle=0, end angle=180, x radius=5cm, y radius=2.5cm]
            -- cycle;
    \path[draw=none, postaction={decorate},decoration={text along path, 
        text={|\fontsize{16mm}{19mm}\bfseries\color{red}|text},
        text align=center}] (0, 0.5cm) arc [start angle=180,end angle=0,x radius=5cm, y radius=2.5cm];
    \node at (5cm, 1cm) {\fontsize{16mm}{19mm}TEXT};
}

}
\begin{document}

\begin{tikzpicture}[every node/.append style={transform shape}]
    \draw (-1cm, -1cm) rectangle (11cm, 9cm);
    \pic[] at (0, 3cm) {Test};
    \pic[scale=0.25] at (8cm, 0) {Test}; %Scales all but the text along the path
    \begin{pgflowlevelscope}{\pgftransformscale{0.25}}\pic at (4*4cm, 0) {Test};\end{pgflowlevelscope} %Scales and positions right, if I consider the scale factor as an additional multiplication by 4.
    \begin{pgflowlevelscope}{\pgftransformscale{0.25}}\pic{Test};\end{pgflowlevelscope} %Scales but no way to set the position
\end{tikzpicture}

\end{document}

I want to scale my pics according to the \pic[scale=0.5] property or something similar. So I have different approaches:

1. `\pic[] at (0, 3cm) {Test};': This is the reference approach, where no scaling is needed. (It can be seen in the image below as the top variant)

2. \pic[scale=0.25] at (8cm, 0) {Test};: As you can see at the image below (variant on the bottom right), the problem with the code is that the \pic[scale=0.5] ... variant scales everything correct, but not the text which is defined as text along path.

3. \begin{pgflowlevelscope}{\pgftransformscale{0.25}}\pic at (4*4cm, 0) {Test};\end{pgflowlevelscope}: This is the variant, which scales everything correct, but the positioning of the \pic is much harder. Because here I have to keep in mind, that in the future the scaling by factor 1/4 is applied, and therefore the coordinates must be multiplied by 4, to position it correctly.

What I want to know, is if there is another approach of scaling which does meet my requirements. (they are scale by a certain factor and also direct absolute positioning without keeping in mind the scaling factor at the absolute position calcuation step).

Answer 1

When I started to write the answer to this question I thought that just putting transform canvas inside the pic will be ok. But then I realized that even inside the pic, the canvas transform scale origin is by default the canvas origin (and not the pic's one). So a simple transform canvas = {scale = ...} displace the entire pic. To overcome this I transform the canvas by scaling around the pic's origin.

\documentclass[tikz]{standalone}
\usepackage{lmodern}
\usetikzlibrary{decorations.text}

\tikzset{
  Test/.pic = {
    \path (0,0) coordinate (O);
    \begin{scope}[transform canvas = {scale around={#1:(O)}}]
      \draw (0, 0) arc[start angle=180, end angle=0, x radius=5cm, y radius=2.5cm]
            -- ++ (0, 2cm) arc[start angle=0, end angle=180, x radius=5cm, y radius=2.5cm]
            -- cycle;
      \path[draw=none, postaction={decorate},
          decoration={
            text along path,
            text={|\fontsize{16mm}{19mm}\bfseries\color{red}|text},
            text align=center}
        ] (0, 0.5cm) arc [start angle=180,end angle=0,x radius=5cm, y radius=2.5cm];
      \node[transform shape] at (5cm, 1cm) {TEXT};
    \end{scope}
  },
  pics/Test/.default = 1,
}
\begin{document}
  \begin{tikzpicture}
    \filldraw[help lines,blue!35] (-1cm, -1cm) grid (11cm, 9cm) (0,0) circle(2pt);
    \pic at (0, 3) {Test};
    \pic at (0, 2) {Test=.5};
    \pic at (0, 1) {Test=.25};
  \end{tikzpicture}
\end{document}