You can tweak swing mechanics, Schmidt noted he changed his mechanics three times in his ML career.
Or look at Schwarber last season, adjustments to make more contact.
On the other hand, Howard couldn't adjust as he aged, remained a dead pull hitter and pitchers exploited that.
The problem came when hitting coaches went gaga over elevation, swinging for HRs isn't a tweak but a total re-invention. And it makes contact more difficult for most hitters.
With Crawford, a slight change in bat angle could play major dividends, you're not trying to turn him into a power hitter, you're trying to turn GBs into line drives. Though with two strikes, with his speed, I'd much rather have him "slap" GBs than strike out.