Bridge too far, I think. Either the device is managed or it's not. If it's not, your app has no control at the level in your example.
"MDM can't control Activation Lock on unsupervised devices. On an unsupervised device, Activation Lock is enabled when the user signs in to iCloud and turns on Find My iPhone."
Remember too, an ML&LM profile needs a certificate from Apple that is only available through the Developer Enterprise Program.
>developing an app for a client
Suggest your client obtain a Developer Enterprise Program account.
I understand this needs to be under an Enterprise account, but aside from that, can what we're trying to achieve be done? Where in we manage the MDM services from our server and anyone downloading our app from the app store can get enrolled from the app? Or am I misunderstanding how device enrollment works?
>anyone downloading our app from the app store can get enrolled from the app?
You're asking if a store app can be used to MDM enroll a device, thus making it managed/supervised so that your app can interact with Lost Mode. Separately, I doubt the former, but once managed, I can imagine the later.
Have you talked to these people?
• 3rd party API? h ttps://simplemdm.com/ios-9-3-lost-mode-per-device-app-deployment-notes/
• h ttps://simplemdm.com/how-to-deploy-ios-apps-for-businesses/