I've noticed that the charging brick gets pretty hot when in use. My advice would be to keep the brick on the outside of the box to keep the heat it produces out of there completely.
That could work for sure, my only thought on leaving it inside is in case it catches on fire. Just saw an article about the CPSC going after chargers now
And why not just introduce a DC inverter with a breaker into the system within the same box as a double-check? Also, attach a thermometer to the outside of the box so you know what you're dealing with. But that's the engineer speaking - "if it's worth doing, it's worth overdoing."
You can have the best Lithium cells, the best battery management systems and you still have a very very low residual risk of your battery catching fire.
I’ve watched a few videos that demonstrate these bags, and they give you about a minute to drag it out of your home at best. There are flammables cabinets made to contain the energy, or you can fashion your own or use a charcoal grille.
Mtb e-bikes are junk as of now. Nothing but electrical problems with water intrusion and corrosion and motors blowing up at 1000 mile mark don’t forget 5 to 10k for a decent one