Yeah I totally see the point of having Asahina Mikuru (Adult) as a tag, but suzumiya haruhi (young) is a litte... too much imo. suzumiya_haruhi younger would already do the job.
Well one issue, which I realized is that there are two official younger variants of Haruhi. The wiki is written for middle schooler Haruhi (7th grade) that appears in Bamboo Leaf Rhapsody (LN and Anime) with the orange shirt with Panda logo and blue shorts (post #36728, post #4625926), which is the most common form of younger Haruhi. There is also an elementary schooler Haruhi (6th grade) depicted in the anime (episode: The Melancholy of Haruhi Suzumiya V) with a pink sweater, white shirt, and red skirt (post #49606). I believe elementary schooler Haruhi is only ever mentioned in the LN, while the anime actually depicted her.
Despite only being a year apart in age, 7th Grade Haruhi normally tends to be depicted recognizably older (imo) than 6th Grade Haruhi who is always depicted as recognizable a loli-type design. Elementary schooler Haruhi also tends to be depicted with more leeway on her attire, but always a combo of red skirt/dress with white and pink top.
7th Grade: post #481976, post #3988646, post #2060218 (although exceptions like post #587572)
6th Grade: post #164943, post #160496, post #182589.
There are of course then depictions of a younger Haruhi without referencing a specific version of her from the series: post #933526, post #193180, post #722209, post #430487, post #637607