Yeah that makes a lot of sense, I quite like it with the Briggs, but like you said you must consider the law. Also doing away with the Briggs and using your electric motor will free up more space in the rear and make it very usable for groceries and such. Nice score!
I see a trike somewhere in my future, but way too many projects ATM, but I have plenty of time I guess. I look forward to seeing what you do with it.
Oh by the way, how big is the electric motor and how fast do you think it will propel this trike?
You mentioned it had 24" wheels, would you consider replacing them with 26's then you could do away with the rim brakes and do a more vintage style build, or do you not plan on getting that involved in this build?