That could be the path if it worked after some testing, basically a one-sided e-ink display configured by high power electric pulses external to the body.
If that doesn’t work it could be possible to encapsulate an off the shelf flexible e-ink display and connect it to an EPC that can be configured over NFC or Qi.
Ultimately though the real question is whether you’ll even be able to see subdermal e-ink. Someone is going to have to try it transdermally like Amal did with a solar panel to find out.