Why do the vast majority of these seem to either block off the 40pin header or convert it to female header that's incompatible with further hats? And why are they full sized, despite having minimal circuitry on them? I can appreciate the ones that build in a cooling system, but that doesn't need to block off all the pins that aren't being used by the hat.
It seems like all this could be accomplished with a small board that doesn't interfere with everything else one intends to do with a Pi or Pi-clone. In fact, I'm surprised at the lack of built-in POE Pi boards out there.
you could litterally achieve this with an inexpensive adapter
edit: it works by plugging a normal ethernet cable, add an 5v power adapter (net, battery, anything really) and at output of adapter you attach an PoE eth cable. An reverse working adapter also exists, if your hardware at the end of the chain needs a 5v input, if needed