I plan on running the lost mine of phandelver. My party size is only two players right now (bard and a cleric), so I want to introduce some recruitable sidekicks they can pick up to help them on their adventures (Sildar joining as a warrior for example). I heard that the BBEG is a bit underwhelming or anticlimatic as a character, so I wanted to introduce them early as a potential sidekick (the rogue type) they can pick up that will inevitably backstab them.
I haven't finished reading the adventure to its fullest. What are some potential complications I should be aware of? Is this a bad idea or how can I make this work?
I'm a new DM with only two sessions completed so far. I've read through chapter 2 and a bit of chapter 3, and it's a bit daunting so far. I'm concerned managing the BBEG as a sidekick will be more than i can handle since it deviates from the material by a lot.