In a comment about this post talking about Takuro Ishii's previous life as a pitcher, Deanna Rubin mentioned another player who switched from pitching to hitting: Swallows outfielder Ryuji Miyade. Miyade was a pitcher for the Swallows up until 2001 or 2002. He then switched to the outfield and has been there ever since. His cards up until 2001 show him as a pitcher. His cards from 2003 on show him as an outfielder (he doesn't have any BBM cards in 2002 that I know of).
Here's his 2000 BBM card (#225) and his 2006 BBM Rookie Edition card (# 125) which shows him both pitching and hitting:
Obviously, Ishii and Miyade are not the first to switch from pitching to hitting. Dragons Hall Of Famer Michio Nishizawa did it among others (including some guy named Ruth in the States).
Then there are those who attempt to switch from htting to pitching, even if it's just for a third of an inning in an all star game: