When you say it pops off and becomes an axe… is this like a wafer-thin flexible piece of metal attached to his chest that stiffens and becomes an axe-shaped blade, or has he got a big heavy axe head attached to his chest all the time?

Because if it’s the latter, that’s just a bit silly, but if it’s the former, that doesn’t even make a lick of goddamn sense. An axe is useful because of all the weight in the head. Anything without that weight would just be a huge pizza slicer.