Who says there can only be one SIM card? What if the user can have her own SIM card? Who says SIM cards are only useful with cell networks? What if the user has her own network? Is that impossible, now and forever? What if she has her own authentication and encryption needs, apart from some telecom's network?

Yes, the telecom owns the card they give you. Indeed, that is their property. But they don't need to own the smart card standard and use it to exclude users from using the slot.

Imagine if the motherboard you bought would had certain slots that were off-limits to you and open to use only by certain companies.

As for "glorified assemler", have you considered something more succinct, like FORTH. There's nothing glorious about Java.