Pretty much all I know about this motet is that the St. Olaf Choir performed it in 2015 and that, like most of his motets, Bach composed this for double choir and string consort. The most interesting thing that I have been able to dig up without actually having gone through the score is that there is a lot of controversy over the time and location of its composition—either in Leipzig in 1726 (as a majority of scholars suspect), or earlier in his Weimar period (suggested by newer research and stylistic analysis).
I may talk about its function as a funeral piece, trying to reconcile its seemingly “jubilant” attitude with the sentiment that Bach intended for it and that listeners in his time would have probably recognized. Its reassuring and comforting demeanor situate it well as a funeral piece, even though it may seem inappropriately upbeat to those who don’t know the meaning of the text.
Another source of research could be other settings of similar text, such as Philip Stopford’s Do Not Be Afraid. There are several verses in Isaiah that begin with this source text, “Fear thee not…” but all of the pieces written from them can be said to share a common thread.
Like I said, musical analysis is going to have to play a large part in this project, so I will likely delve into the significance of the two choirs’ interactions with each other, the role of the strings, and the overall deftness of Bach’s setting. Score analysis is everything in a paper like this. Like David said, it’ll be a struggle to turn “Bach is cool” into a legitimate thesis.