In my bus conversion, I'm planning to go the spray foam route. The prices are close to the same, the R value is close to the same, and the spray foam will fill cracks and help stop all the air flow issues traditional insulation runs into.
As for the fire safety aspect, I'm personally considering Tiger Foam
, which has a fire rated version.
Good luck with your remodel project. I hope we get to see some of the pictures as you go along.
I hope this information is helpful to you,