Jaheira's quest leads straight to him,I think you need her to recruit him as he trusts her and she convinces the emperor to save him not you. He is great, he sounds and speaks like Minsc, not in a repeating the same lines he said in BG2 like Jaheira does but in having original lines that are 100% Minsc

Minthara is the best character and she NEEDS to be recruitable if you side with the grove!
Also- I support the important thread in the suggestions: Let everyone in the Party Speak