I would like to propose an omnibus "Germanic Languages and Dialects" category. The category would have tags that can help scholars link specific Germanic languages, dialects, their grammar, syntax, and related vocabularies
My reasoning for this proposal is this: the Germanic languages are either similar or closely related; this proposed category would make it possible for scholars and others to take all questions and answers related to the various Germanic languages (e.g., to name just a few: high/low Saxon, platt-Dutch and German, West Belgian/Afrikaans (Flanders), Hollandish, Frisian (all dialects), Zeelandic, Alemannic, Faroese, and the Batavian the Chamavi, Tungri, Ubii, Bructeri, Cherusci Germanic tribes and other Gothic/Tuetonic tribes in Germania Magna, Germania Inferior, and Germania Superior alone, and putting them all under one 'allgemein' (common,general) roof for ease of comparison and learning.
One of the valuable features of a Germanic languages and dialects forum on StackExchange is that the many maps that are available showing the geographic locations and significant movements of Germanic language groups during or over relatively large time periods an be included in questions and answers to more easily illustrate the "where and when" of Germanic language groups and their spheres of influence and movements. Additionally, the Wikimedia Commons website can provide maps and other illustrations used in a Wikipedia article to help users visualize questions and their answers.
The alternative of not having a Germanic-languages QA forum is to have the various languages (and their dialects, too) located in individual language-specific sites scattered all over the StackExchange landscape, as would be the case if the current specific language->website format were to be followed.
By way of comparison, there are only eighteen on-line Germanic language Wikipedias available for Germanic language review. None of those Wikipedias offer the kind of interactive Q/A forum for scholars and others that could be made available in StackExchange under a new "Germanic Languages and Dialects" forum. In fact, with a Germanic languages.StackExchange.com the articles and Talk pages in those eighteen Wikipedias would surely be the source for a great many questions that could be asked -- and answered -- by StackExchange members.