If you want to allow users to install an app offline, sending the APK file over bluetooth seems like a reasonable way forward. Regrettably, and without any real documentation the issue, some versions of Android block this. Perhaps it's anti-piracy.
APK receive over bluetooth was blocked on:
- Nexus 4 (Android 5)
- Nexus Galaxy (Android 4.3)
- Yoga Tablet 2 Pro (Android 5)
- Samsung SM-G313F (Android 4.4.2)
- Wileyfox Swift (Android 7.1)
- Moto E2 (Android 6)