It's not like the potion is an exact science though. It does essentially link Erik's mind to Alexi's, so it would be logical for there to be some unexpected repercussions with that. Maybe not severe ones, but I think we could work out a few faults in the whole thing, while keeping the main idea. It's less fun if things work perfectly as intended.

Ahh, when he said he wanted to protect Joseph, it made me (and therefore Erik) think that he was going to try and administer it on his own, which would be a hilariously bad idea for Alexi. It's becoming more and more difficult for Erik to see him as a person and not a piece of meat, made worse by the fact that they aren't exactly friends at the moment. The funny thing is, normally Erik is very respectful of humans. He isn't a "Vampire or Magical Supremacist" he just wants everyone to be equal. He worked with abolitionist humans in the rebellion with no problem. But the deprivation of blood does crazy things to a vampire's brain... and again, it doesn't help that he hates Alexi for chaining him up like this and is only even being civil out of practicality.