Formatting error bar mark pgfplots, append to style?

I am trying to increase the thickness of my error bars. I found that the stem and the marker needs to be changed individually here. Problem with this is that using /error bars/error mark options={*styles} I am overwriting the defaults which gives me no marks to begin with. Trying to use /error bars/error mark options/.append style={*styles}, however, compiles fine but has no effect, neither does .prefix style={*styles}. What am I missing?

documentclass[]{standalone}
usepackage[]{pgfplots}
pgfplotsset{
    error bars/error bar style={opacity=0.7,ultra thick},
    error bars/error mark options/.append style={ultra thick,red}} %does nothing
begin{document}
    begin{tikzpicture}
        begin{axis}[
            mystyle/.style={thick,mark=square*,only marks ,error bars/.cd, y dir = both, y explicit}
            ]
            addplot[mystyle] table[x index={0}, y index={1},y error index={2}]
            {
            0 1 0.5
            1 1 0.5
            2 1 0.5
            };
        end{axis}
    end{tikzpicture}
end{document}

On another note, I find the design choice of the error bar styles a bit cumbersome in the first place: why is there is no high-level command to change the thickness of the vertical and horizontal portion of the error bars at the same time? But rather they need to be changed individually. Maybe a suggestion, it would be nice to combine more styles and make it the default behaviour to change both by using error bar style, then make the styles individually accessible via error bar mark options and error bar stem options or something of that sort. It’s just my impression, but so far I have seen mostly examples, where the stem and the mark have the same thickness, so that seems to be the default for most people – myself included.