Regular wings used to be done as OAF back in the day, even non-detachable ones.
Restrainable (-½) plus Only in Alternate ID (-¼) would do for their harness version without needing to involve Focus. You end up with -¾ worth of limitations, which nicely straddles the cost between OIF and OAF.
Yeah I thought of that, but in several stories where the JLA/JSA were captured, Hawkman would lose his wings but not his mask. So the villains knew it was a focus. Even with this reasoning, OAF and OiHID are both valid builds and I have no problem with them.
The only problem with OAF is that it can be taken away with a successful grab and disarm. Kind of like gas masks you see in movies and comics where the villain comes up and pulls them off the agents.