I have sat my 3A+ inside an altoids tin and it does kinda fit... but it takes up more than double the space that the zero does. You'd have to depopulate the board, use a different or custom PCB, and still likely have to sacrifice battery size and audio. Not to mention that the 3A+ draws considerably...

I am super excited to see this thing become a reality! I literally joined the forum just to see if there were any updates on this!