I see that the plan seems to be creating a parser function for choosing page images on a page, phab:T91683.
As a passive observer that has used other wikis before, I'd say that this is a pretty massive mistake of simply repeating history by putting metadata into the article. Categories are a great example of a tool which has massive problems because of this:
- Localization is impossible - A category is really just a tag, but because it is embedded in an article it can't be translated without massively duplicating the data
- No stable id- This causes several issues, it can't be removed or renamed without needlessly editing every single article containing it
- No centralized GUI or curation tools to manage it
- Performance issues - Phab:T116001
The same thing will be repeated if this is added as a parser function for setting page images:
- Parser function on each article - on 100000 articles, every single article will need to be edited to remove or change it
- GUI or better tools - this would make it once again hard to choose or change images using mobile devices
- Duplicate work - A bat would use the same image, but this would need to be set on every article on every wikipedia, instead of using and encouraging something like wikidata
- Complicated parser function + wikitext - people will likely add parser functions within it, and use hacks like "{{#tag" on it
About the only benefit is setting these images using templates. That in itself is a problem because templates are complicated beasts. This could be done way better by using simplified GUI based decision trees.
Unlike categories, images can be understood by everyone and many people can help out to choose appropriate image for articles. Anyway, this parser function path seems to be already set, but perhaps one day it will be revisited.