Simmons is the best defensive SS in the game. He saved like 35 runs on D alone last year. There is a very good reason Wren doesnt want to give him up.
Yes obviously I'm not saying its dumb to not "want" to give someone up. It's dumb to not even consider it. He may have had the best defensive season ever but he was still negative on the base paths and had a wOBA of .303 meaning he lost about 10 runs combined.
He's a great shortstop, "untouchable" I think not. Also you're implying he'd being giving him up for nil, would not happen. Wren just isn't very opportunistic to me, keeps his guys until they prove they are unproductive (Tommy Hanson, Jurrjens). They're a winning organization, just a different mindset than I would have. You could argue the Upton trade here but if anything that's about a wash right now, unless you see Chris Johnson as real.