The canary in the coal mine here is that you have to keep practicing language or you lose it. All of that effort is admirable and intellectually interesting but if you have no one to regularly speak with when you leave China, it's not a good use of time and effort. Unless one never wants to return to their home country, or marries a native. He's right about French. It's probably my favorite language, I lived and work…
I study French, German and Russian at Uni. I am completely with you. As much as I love the French language, I will not keep up my knowledge of it after graduation. I've rarely had a positive experience of real french use, compared to almost every time with Russians and Germans.