I think it can be as simple as... "I was thinking about what you said, and you were totally right, if we <insert your idea> then we can achieve <insert their g

I think it can be as simple as... "I was thinking about what you said, and you were totally right, if we <insert your idea> then we can achieve <insert their goal>. I'm really glad you said that - you really gave me a new perspective on this."