First, I didn't say Boston should build around Lin or Asik, I said they were assets, which they are. They are young players with 2 years left on their contracts. They are easily movable at any time.
Second, I don't know where this notion that Lin is terrible came from. In his third year, he averaged 13.4 p, 6.1 a, 3 r per game with respectable outside shooting for a PG. I mean he isn't Rondo, but he is far from terrible.
Third, double double centers don't grow on trees. They aren't easy to come by. Asik is a double double center and while he isn't young, he did just finish his third year so he will only get better.
This would be a pretty solid trade for Boston. Two good solid young assets for a PG coming off of a torn ACL is a pretty solid trade.