Not sure how realistic it would be, but could you have the offline mode place temporary UID which would be replaced the next time they go online?
Welcome,
Please use this board to share custom content files for the D&D3.5 and D&D5e applications for android.
Official content for 3.5 can be downloaded here: View Thread
The 3.5 app can be downloaded here:
The 3.5 app can be downloaded here:
Online Content Creator for 3.5
To create content for the app which can be shared on this forum use the new Content Creator!
Official content for 5e can be downloaded here: View Thread
All content in one file can easily be downloaded here:
All content in one file can easily be downloaded here:
Download: 
All content db.dd5 --- [Open in app]
Online Content Creator for 5e
To create content for the 5e app use this content Creator.
Online Character Manager for 5e
New! Manage your characters online for the 5e app!
Read the latest review of the Complete-Reference app
