But you can stamp and sign such cards
And you know Indians loove to stamp and sign stuff.
The only similar overseas citizen scheme I know of is the mavi/pembe card issued by Turkey to migrants who pick up citizenship in other countries. Sadly they named it blue card recently, so its impossible to find images of it in the interweb easily. I vaguely recall from my last trip to Turkey that my collegues looked like a service passport in a similar format to the OCI card. The images I see on the internet are more of a card but all in Turkish and very rudimentary.