My group has houseruled (and yes, it is a houserule) that you get the benefits of the squirrel loophole without actually needing the squirrel: That is, you can cast Hex on nothing in particular, and then transfer it as if the target was dead. Sacrificing a critter every morning is thematic for some warlocks (say, fiendish ones), but not so much for others, and if your group decides that that's a reasonable level of power for warlocks to have, it should be available to all of them.