Only 1 (major) problem.

Since you have to sign 2 transactions before sending the liquid Hive, what happens if:

1. Person 1 enables SPI on his account (active key multisigned thus 2 firms to allow tx).

2. Person 1 + SPI sign together Power Down tx (everything Ok until this point).

3. Then you (SPI) have to send the Liquid Hive.

But... what happens if the provider of the service (in this case SPI) refuses to send the liquid Hive?

Then you have a Power down enabled WITHOUT the ability to revert back the tx (since you need now 2 signers).

(Well, thinking about it as I write this you might reset the full set of keys with the owner, but this is a very sensible tx and 99% of users aren't really familiarised with it. )

You see the attack vector? If SPI goes rogue, things can go bad real fast (but well, in that particular case SPI has much more to loose Vs the end user).

Kindly regards :)