Is this somehow possible?
Yes, but the steps depends on your wallet type.
If you have
Standard wallet, doing what others said is the precise way to do this.
If you have a
2FA wallet, you'll have to restore a 2-of-3 Multi-Signature wallet containing all three master public keys (
keystore1, 2 , 3) from your wallet information.
The order of the master keys doesn't matter in Electrum.
He has an Electrum wallet already on desktop, he can only have 2fa on mobile, he can not have electrum on mobile because it is not food to have both the authenticator and the wallet together. He is good for him to just go for watch only wallet. I get what you are saying that on 2fa wallet, that he will not be able to spend but it is not what he is looking for.