I don't like it. You only have 4 RB as it is, and making this trade leaves you with only 2...and the 3rd is a banged up Benson. Ewww. While sure, your two starters would both be elite, you're setting yourself up for failure should one of them go down. Also, Morris is performing at an elite level right now anyway...no reason to ship him off just yet! Sure, he's a Shanahan RB, and I get that...but ride the Morris wave while it's still hot! Doug Martin is necessary insurance for you IMO.
I'd be looking to ship out some of the WR depth you've got. Once Nicks is healthy, you'll have more WR than you can start. And why no backup QB?
Help with mine? viewtopic.php?f=18&t=524925