I agree with all your concerns, Mao - I guess its not like Cruz provided much defense lately, of course. The idea of Tracy's arm in RF is worrisome (of potentially hurting it, too)- Geez - Gonzo, Green and Tracy - has to be one of the weakest defensive OF in the Majors. They'll be tested by every runner, that's for sure.
If they try to encourage Conor to go after big hits, it'll backfire, although I'm sure that'll be in his own head too. However, if they put him leadoff or second, or low in the lineup initially, and just tell him keep being an OBP machine, it has to help the offense some. We'll see if Melvin has a realistic read on Conor's abilities or not. And I suspect the FO will be watching how he handles this rookie - of all the prospects, Conor is probably the most ready, resilient and mature, so he'll be a very good test case.