Managed to get my entry in with 10 minutes to spare (was originally planning on spending the whole evening on this but ended up taking the gf out for dinner... priorities, priorities...)
Need to get you your prize!!
No dependencies required, just have your plugin serve templates (add the template option into plugin.json), and in that template folder, have a folder called emails, and place your template in there.
Also place a corresponding plaintext one with the suffix _plaintext.