The eye is real. No one is disputing that, but remember that not only does he not have a lot of power, but completely in contrary to what you say, gap power for a switchie who will mostly bat lefty does not translate well into Fenway unless the hitter is an oppo power guy.
As for the rest of your point, a sub-.735 OPS he may not become. He may also not become a "below-average by positional standards" hitter (even though i doubt the AL average OPS for LFers is .735, but i digress). But his lack of skills other than OBP without speed and middling defense don't make him a starting option on a contending team, but rather a good backup.