It wouldn't be trivial, you'd need to open them up and find some space for the unit inside, wiring the + and - to the driver. You'd need to mod the case to connect the charge points to something on the outside to charge them. Having these modules in there could affect the frequency response too as it's an open back.

Someone did a very involved mod with the TRN BT20S Pro and the HD660S, which involved 3D printing a load of parts and re-fitting these into them

/r/headphones/comments/10h4psm/second_iteration_of_hd_660s_bluetooth_adapters/

Even in this case though it would be easier as the 660S is at least a dual sided headphone to start with, the HD560S is single sided so you have two mono adapters (for L and R) but you only have a port on one side. So you'd need to get more involved than that and I think re-wire it internally.

If you're super into modding/DIY projects. But it's not some easy thing to make this work.

Easiest way to make the HD560S work, as it's single ended, is use a single cable output stereo BT adapter and plug it into the one side, and then tie the adapter to the headband or something.