Would this make it easier to lose coins from human error? What happens if you lose your phone? Is it possible to allow very slow draining of a wallet with access to just one of the two private keys (e.g. max of 1 coin sent every 100 blocks)?

This way coins could be recovered even if one of the two factors is lost. It would also reduce user inconvenience for cases where security is not as essential. However, it would still be possible to steal very slowly.

Residing in a country where you need two factor authentication for everything. I suspect that this modification (while very useful) could impose serious inconveniences on users if poorly implemented.