Can't say if it's smart move when it comes to fighting-side of the rematch, McGregor seemed a bit surprised at how well Diaz took in all the shots so if he can't add some more firepower in his arms and try to knock Diaz out, it's gonna be an uphill battle. On the other side, I think it would hurt his image more if he just leaves this loss as it is and moves back to Aldo.
In my opinion, each day he keeps himself training for 170 makes it harder and harder to go back to 145, even the last time he looked completely drained and half-dead at weigh-ins.