This is a terrible, TERRIBLE idea. Especially for people who move a lot. Phone numbers get reused. I am currently maintaining 4 SIM cards just to keep services relaying on them active. About 2 months ago I forgot to recharge one of those SIM cards and was locked out of one of my bank accounts.

Why don't you register all services with one SIM and use a Dual-SIM phone to get cheap rates on another card?

Since we are talking about introducing a new identity system, isn't it easier to resolve the problems you mentioned than to introduce something new?

Because some services (banks) restrict phone numbers to only local (same country) ones.

India has a sim card system like this, but it is actually even less secure and shockingly easy to game. That's not even counting for the fact that not everyone has a cell phone (a minority, but still exists).

How do you game it apart from stealing a phone? It may be easy to get another identity but that's a feature.

If somebody commits a serious crime, the joined location of the phones will reveal the true identity unless somebody invests an amount of effort that's equal to buying a new passport.

I imagine sim swapping is a thing over there as well, maybe even easier to do than in the US.

So you get several identities. How do you game the system?

Intelligent agencies have failed to keep their phone usage cleanly separated. It's not that easy.

E.g. if you want to avoid progressive income taxes by registering several companies, your burner phone stands out because it doesn't have any other contacts. That will be further investigated.

Then you need the name of a living person who doesn't use a mobile phone to register it because otherwise, he would operate two phones at two different places. Another red flag.