Customize biblatex windycity style

I'd like to customize windycity, which is a biblatex implementation of Chicago Manual of Style's 17th edition. If for some reason, windycity is very difficult to customize, I'd settle for customizing the default biblatex-chicago style.

What I would like to change:

1. The first time anything is cited, if it has a shorttitle, the short title should appear in the note after the title in brackets. I'll show examples below.
2. In the bibliography, anything that has a shorttitle should also show the short title in brackets in its entry. Again, I'll show examples below.

(If anyone cares, this is basically the style for Oxford Studies in Ancient Philosophy. See sections 6 & 7 on their submissions page if you're even more curious.)

MWE:

\documentclass[12pt,letterpaper]{article}

\usepackage[style=windycity,backend=biber]{biblatex}

\begin{filecontents}{mwe.bib}
@book{ nails2002-people-of-plato,
author = {Debra Nails},
title = {The People of Plato},
shorttitle = {People},
publisher = {Hackett Publishing},
year = 2002,
}

@article{ morrison1942,
author = {J.S. Morrison},
title = {Meno of Pharsalus, Polycrates, and Ismenias},
shorttitle = {Meno},
journal = {Classical Quarterly},
year = 1942,
volume = 36,
number = 1,
pages = {57--78},
}
\end{filecontents}

\begin{document}
Blah, blah, blah.\footcite[][15]{nails2002-people-of-plato}

\printbibliography
\end{document}


Examples for citations:

• The first citation of the Nails book should look like this:

Debra Nails, The People of Plato [People] (Indianapolis, IN: Hackett Publishing, 2002), 15.

• The first citation of the Morrison article should look like this:

J.S. Morrison, “Meno of Pharsalus, Polycrates, and Ismenias” [“Meno”], Classical Quarterly 36, no. 1 (1942): 59–60.

Examples for bibliography:

• Morrison, J.S. “Meno of Pharsalus, Polycrates, and Ismenias” [“Meno”]. Classical Quarterly 36, no. 1 (1942): 57–78.
• Nails, Debra. The People of Plato [People]. Indianapolis, IN: Hackett Publishing, 2002.

I've read several other questions about customizing biblatex, and my guess is that I need to create a personal biblatex.cfg, but I am not sure what to add there.

Since windycity is an extremely modular style it is enough to redefine the bibmacro longtitle. Its original definition doesn't contain the \iffieldundef{short\xtitle title} block (see ll. 1167-1173 of windycity.bbx in version 2019/07/17).

\documentclass[12pt]{article}

\usepackage[style=windycity,backend=biber]{biblatex}

\renewbibmacro*{longtitle}{%
\printtext[\xtitle title]{%
\printfield[noformat]{\xtitle title}%
\iffieldundef{\xtitle subtitle}
{}
{\subtitlepunct
\printfield[noformat]{\xtitle subtitle}}}%
\iffieldundef{short\xtitle title}
{}
\printtext[brackets]{%
\printfield[\xtitle title]{short\xtitle title}}}}

\begin{filecontents}{\jobname.bib}
@book{nails2002-people-of-plato,
author     = {Debra Nails},
title      = {The People of Plato},
shorttitle = {People},
publisher  = {Hackett Publishing},
year       = 2002,
}
@article{morrison1942,
author     = {J.S. Morrison},
title      = {Meno of Pharsalus, Polycrates, and Ismenias},
shorttitle = {Meno},
journal    = {Classical Quarterly},
year       = 1942,
volume     = 36,
number     = 1,
pages      = {57--78},
}
\end{filecontents}

\begin{document}
\null\vfill % just for the example
Blah, blah, blah.\footcite[][15]{nails2002-people-of-plato}

Blah, blah, blah.\footcite[][24]{nails2002-people-of-plato}

It is enough to simply add this redefinition to your document preamble. If you want to, you can add it to biblatex.cfg, but that seems more hassle than it is worth.