As it turns out, Apple has a solution in the form of facial recognition. As spotted by 9to5Mac, it seems that Apple will be using facial recognition as one of the ways that users can validate themselves when they add an ID to the Wallet app.
According to the description of the validation process, “Next, take a photo of yourself. This photo will be matched with your photo on file with [ID card]. Now close your eyes until you feel your iPhone vibrate. […] Now open your mouth until you feel your iPhone vibrate. […] Now raise your eyebrows until you feel your iPhone vibrate.”
That being said, it is unclear if this will require an iPhone that has the TrueDepth sensor built into it, or if the front-facing camera is enough to help verify the user against their ID’s photo. Either way, it’s a good way to ensure that users don’t add IDs that do not belong to them.