TikZ：如何在“路径图片边界框”之外的“路径图片”环境中绘制

Question

有没有办法在环境之外进行绘制path picture bounding box？path picture（出于理论兴趣。）

\documentclass[a4paper]{article}
\usepackage{tikz}
\usetikzlibrary{backgrounds}

\begin{document}
\begin{tikzpicture}[gridded]
\fill[yellow] (0,0) circle(10pt);
\fill[orange] (3,4) circle(10pt);

\node[draw, thick, minimum size=3cm,
path picture={
\fill[red, overlay] (path picture bounding box.west) coordinate(X1) circle(2pt);
\fill[red] (3,4) circle(3pt);% not shown
},
]{a};
\end{tikzpicture}
\end{document}