I get what you're saying but it's never a good idea to bet on the exception and not the norm. There will always be anecdotal evidence (Travis Shaw) to justify why guys like Tzu-Wei Lin will play exceptionally well at the MLB level. But more often than not guys regress to what they are.
Also, it's important to not that Shaw could always hit, he had a .803 OPS in the minors and currently his MLB OPS is .809. The question with Shaw was if he had the bat speed to carry his hitting tools to the next level, and it looks like he does. Sometimes guys have other qualities that we just can't quantify, who knows what it is with Shaw....maybe he's just really smart and able to overcome that deficiency.
Wei Lin is currently sporting a .877 OPS in 46 PA's after 6 seasons in the minors with an OPS of .638. It's extremely, extremely likely his MLB line going forward at some point is going to represent the .638 if not worse. Things change, this isn't set in stone, but he's not going to BABIP .448 for the rest of the season.
I'm a big fan of riding what you got, catching lightning in a bottle, going with the trend, or however else you want to put it and Lin plays the position fine.
But at times this teams lack of offense has really shown, and if there's one place we can use an upgrade.....it's at 3B. Perhaps Lin stays hot long enough for a guy like Devers in a month or two, but I'd be very uncomfortable if Lin is our 3B going into the post season.
If I'm wrong, and he's sporting a .877 OPS come October I'd gladly eat some crow. You guys can shove a big old plate of crow done my throat. It's exciting to see guys defy the odds but hedging your bets at 3B could pay dividends when it comes to trying to win a WS this year.