I hope Barcus Wroot will be a companion, I like him. He is very loyal to his friend Wulbren, and very brave to initially try to reach Moonrise Towers by himself - I think he could definitely be one of the "good" companions.
Barcus describes himself as an alchemist and tinkerer, so arteficer was the first class that came to my mind. I know this is not a class from the PHB, but it would be nice to have one in BG3.
