Multiple numbers is already technically possible and does not require eSIM. It does require the carrier to innovate and actually do some engineering though, and there's no market pressure for them to do so.

Vodafone UK still associates your contract with a phone number. That is, if you wanted to keep the contract and re-associate your phone number with a new contract that is not possible without paying for the remaining months on the contract.

Potentially, but my point is that it's a commercial decision or incompetence (maybe the number is used as the primary key for the contract record?) - technically there is no reason for this.

It’s incompetence driven by the market conditions: nobody on the market can do that and therefore no one is motivated to do that. I can understand that maybe not many customers ever need this too. AFAIK the engineer on the other side of the call said nobody provides such a service in the UK.

FYI, iPhone 13 generation devices already have 2 eSIMs, as in you can have dual standby without a physical SIM. I'm not a fan of this direction but I don't think we're going to lose dual SIM support.

I haven't thought about this too deeply, but I was thinking if you can have every phone come with "free" global network access - just data. i.e. get rid of the current tech for voice calls, so that all phone calls will be over a VOIP type service. And you can't use the phone without an active account with one of the providers that participate in this global access program. Each provider can bill other providers on the backend when a roaming subscriber uses their network.

This is exactly how I imagine it would work, albeit with a standard provision being made by Apple and Google as a starting point, something like a universal federated VOIP (they'll come up with a decent brand name for it obvs). If you're on Android you can get UFVOIP in your Google One subscription, or with Apple I'd assume it would be an iCloud+ feature. And then obviously slick contacts integration at the O/S level so that it's seamless to add a new contact - something like when you want to add someone you click "Add Contact" and it gives you a QR code for them to scan on their device to add you.

This could even generate a new relay e-mail for them in the same process so that a single QR code gives them the name and both a unique-to-them phone number and e-mail address to contact you, and adds it to their contacts automatically.

Sharing of contact details could be done by a side-channel:

1) Someone I already know and trust asks to share my contact details to a third party.

2) I get a prompt on my device asking to confirm I want to connect with this new person.

3) A diffie/hellman exchange sets up a secure channel between myself and this new third party.

4) We both confirm we want to add each other.

5) A unique e-mail address and phone number is generated on each device and sent across the channel to the other party.

6) Both parties have now established a new contact for the other party with contact details completely unique to them.

This would entirely resolve a whole class of issues around data protection/harassment/privacy.

If anyone at any time wishes to rescind contact permission they can just burn that contact link. Sure, you could be contacted via someone else that also knows both of you but there's a massive disincentive to pass along your details without your consent - you'll know who passed along your details because they'll be the same unique details you issued to someone else, and you can freely burn their contact link too.