The initial plan with Jacobs is not to automatically platoon him when a left handed pitcher is on the mound.
Manager Fredi Gonzalez has every intention to start Jacobs, regardless of the pitcher.
"I'm not going to play the lefty-righty stuff with him," Gonzalez said. "If it's his turn to play and there is a lefty starter, he's going to play."
I'm completely in favor of this move, assuming Jacobs is healthy, and all reports indicate he is, then it is time to find out whether he can hit left-handed pitchers in the majors. I suspect he can but it still has to be proven. If he can - Great! If he can't - it's time to look elsewhere for a long term solution to first base. But he deserves a majority of the season to prove whether he can or can't.