Well, its still basically those two options if you want to self-custody, and from a technical point of view, I'm not sure its possible to have a better way without extending trust to a third party... So for example, you can do multisig with BitKey, and they will store one Sig on your phone and another in the BitKey's cloud and you can store the third securely.

The point is if you want another way, you basically need to abdicate responsibility which means assigning trust. Its your choice how much you want to do that. You can let Coinbase hold all your keys and not deal with any signatures... Or you can do a multisig and give two+ to people or organizations you trust, or you can do single Sig and take full responsibility and not have to trust anyone else.

That's your choice.

You can store these multiple or single signatures in multiple ways. I like seedsigner method for example, and a backup seed phrase stamped in steel washers with Blockmit.