There is nothing to be done.
Don’t
It seems like an expensive project to implement, that will be mostly redundant with existing smartphones. What would this be able to do that isnt achievable with the current mobile wallet loaded on whatever custom phone?
even
You can certainly still sign txns without the internet on the existing mobile app. The only difficulty is in broadcasting to avoid concepts of double spend. How would your approach allow someone to broadcast something to the internet without internet access?
try