In reply to Thomas.

This issue has been solved by third-party plugins, e.g. Toolset and Metabox. Both offer taxonomy term custom fields.

While it would be very cool to have such a feature in the core, I also think the developers of such advanced plugins should continue to be able to profit from their hard work. They also contribute to the success of WordPress and play an important role in the ecosystem. If the core incorporates too many of their features, they might lose customers, which would not be good for the ecosystem.

Those plugins are not limited to a single image feature. I also doubt the existing free alternatives for that feature have put a dent into profits.

I understand the argument, and it has been made throughout WordPress's history about one feature or another. I have yet to see it have any real-world negative impact (though there may be some examples I don't know about).

On multiple occasions, WordPress has added features that were available in themes and plugins that I have built. For example, my early themes were some of the first to support post featured images. By adopting that feature, WordPress didn't hurt me at all. It made it easier to support my products by having a standard system. I even went on to extend it to offer even more options not available in core. Plus, the ecosystem has benefited from the feature being available to everyone.

Almost every feature you see today in WordPress has existed in some form or fashion in a plugin or theme. To make the argument against adding a feature because a third-party developer has already solved it is to make the argument to never build anything other than, maybe, APIs (of course, there are some folks who would love that).

Anyone with more advanced requirements can simply extend WordPress with Toolset or Metabox to have a powerful CMS.

Unfortunately, that is not the case for everyone. For example, if a developer wanted to build a theme that showcased a featured category image in a Cover block (as shown in the post above) and release that theme for public use on WordPress.org, there's no way to do that without it being supported from core.

Maybe some DIY, tech-savvy users could recreate that using something like Toolbox or Meta Box, but the majority would miss out.