Unless you're playing in for a bunt the balls come at you just as hard at 1B as they do at 3B, when a lefty is up. The biggest difference is having to throw, and he has a good arm, but he might take too long to throw which could be a problem.
Even if the chances of it working out are almost none, I'd be fine with him getting some time there since we're just using a stopgap otherwise for the rest of the year.