From the perspective of a practicing senior EM resident and former EMT, while epi plus glucagon may sound intriguing from a physiology standpoint, this combination is not realistic clinically.
First, physiologically, I would be very concerned about the cardiovascular side effects of epinephrine. Consider the usual indications for subQ epinephrine, cardiovascular or respiratory collapse following an allergen exposure or an exposure previously known to cause cardiovascular or respiratory collapse.
Second, in current times, practitioners would be exposing themselves to medicolegal risk if they just started using medications for indication that may be biochemically sound, but never actually tested inclinical trials. Of course there are many off-label uses for many drugs, but itis always risky to be that trailblazer. People at the frontline always argue whats the difference if the person is going to die anyways. Unfortunately, that defense usually does not pan out. For example, lawyers would argue that the hypoglycemic grandmother would not have had a heart attack if you hadnt given epinephrine and instead waited the extra 10 minutes for a more advance level of care to arrival.
Keep up the innovative thinking though, maybe you will be the trailblazer to start the glucagon + epi movement. 🙂