Seems to me the mosaic tiles would be like hiding from a BB gun behind a chain link fence.
Lots of cracks there for a bullet to slip through at any point there is a crack.
It has been done already, with Dragonskin. They had overlapping ceramic discs but there was a problem with the adhesive used to keep the discs in place. There were also legal issues which meant it could not be DOJ approved.
But the imbricated layout was sound.