I got some inspiration while reading a forum post by Erokow32 in which it was postulated that a familiar could use spell storing rings to cast and concentrate on spells for the caster. I started thinking about how in alot of TV shows, books, and games there is an evil caster who has their familiar pet using some spell in the background while he/she goes about their bushiness. This idea of getting your arcane pet to aid you in performing spells seems very Warlock-like to me. 

So, this gave me an idea for a new Eldritch Invocation requiring that you are Pact of the Chain. The invocation would work as follows:

While you are maintaining concentration on a spell, you can use your bonus action on your turn to transfer the spell to your familiar, which will maintain concentration on the spell in your stead for the remaining duration. The familiar must use its Action each turn to maintain concentration on the spell and otherwise follows the rules for concentration as normal. You can use your bonus action again to regain concentration over the spell. 

I think this would be a really fun way to make use of a familiar and give Warlocks some more versatility in how they choose to cast their limited amount of spells. 

Do you think I should put a level cap on the spells that can benefit from this? Can you think of other ways to improve the language or effect? 

All input is welcome.