Halon found wide usage originally in computer rooms...when computers were big enough to have their own room...1301 was the flavor of choice while containing it within an enclosed space. Humans were invited to leave rapidly. Aircraft used a different flavor, I've forgotten its number, primarily for engine fires. It was considered more of a health hazard than 1301. Strangely the NFPA at some point dropped its health warnings. Maybe you can get past all of the logistical problems already discussed above and use a larger and cheaper ABC extinguisher. However, using Halon in an enclosed engine compartment with an automatic or manually activated system seems the safer and more effective choice.