What about Old English?
Old English is a beautiful and widely unknown language, and most people (including me) were exposed to it by reading Beowulf. I have a friend who speaks and writes it (he asked a college professor for help), and it's quite impressive. Native English speakers should learn where the original language they speak every day derived from. I will ask my friend if he can help contribute if it is created!
The English language changed enormously during the Middle English period, both in grammar and in vocabulary. While Old English is a heavily inflected language (synthetic), an overall diminishing of grammatical endings occurred in Middle English (analytic). Grammar distinctions were lost as many noun and adjective endings were leveled to -e. The older plural noun marker -en largely gave way to -s, and grammatical gender was discarded. Approximately 10,000 French (and Norman) loan words entered Middle English, particularly terms associated with government, church, law, the military, fashion, and food.
There are some remnants in Modern English though. While it is true that English grammar has many peculiarites (for a Germanic language, and word order isn't the only peculiarity at all), it is still very Germanic at its core. And (most of) the parts which aren't typically Germanic aren't really typical for any other language family either (apparently it has been influenced in some instances though, e.g. by Celtic languages).
I once spent a few months "playing" with learning Latin, and learned a very minimal amount of old English in a survey course. The trouble with both, I found, is that they ceased growing when they stopped being used, so are useful only for studying the literature and the world in which they thrived. Great, if one really loves the poem Beowulf (or other works of old English), but of limited applicability to the modern world. I doubt you can ask anyone to fix your computer using either Latin or old English. ;)
The vocabularies of both continue to be expanded to match the needs of the modern world. You can find articles in OE on subjects such as the automobile (https://ang.wikipedia.org/wiki/Selff%C4%93rende_w%C3%A6gn), for example, and the Vatican and Wikipedia (https://la.wikipedia.org/wiki/Autocinetum) have modernized Latin words.
Chaucer's Canterbury tales is a good read. If you're a native English speaker or have a good command of the English language it's an easy read. I read it in university many years ago. https://en.m.wikipedia.org/wiki/The_Canterbury_Tales
Learning old English is like eating pizza without the cheese/toppings. German is a lot more worth while(pizza with toppings). But if someone wants to go at in creating a course good luck.