Stars never draw full value in a trade (see Shaq, McGrady, Vince, Baron). I don't know about Seatle offering Lewis/Allen, since Allen isn't young and has around $80 Million left on his contract. And, your right, Dodigago, Detroit can't break up a competitor, imagine if they didn't play well after the trade?
I don't know if KG will demand a trade or not, but if he does, Petrie should go after him harder than anyone else. Most players are replaceable. KG isn't. There isn't much I wouldn't trade for him, but I would like to keep Miller.