We've talked about Matthews vs Robinson, and I get your reasoning. I don't agree with the conclusion, but that's a different thing.
I have a tougher time with Martin over Lewan. Lewan is as refined as you'd like, and he has the much higher upside. As I've said, Lewan reminds me a lot of Joe Staley. Martin's versatility would be a welcome addition to a line littered with holes, but I wouldn't pass up a high-end LT for him.
I'd be happy with Trai Turner in the 4th. You've noted the risk, and it's legit, but he has All Pro upside, and he has some good tape - especially in the running game. Great scheme fit, too.