Somebody mentioned Jack Cust. Like yeah, that could happen. That's in the realm of possibility. We cut Stewart, and he catches on somewhere and has 3-4 year run as a valuable DH. I'm pretty sure that isn't happening, but it might.
The thing is, he may field like Cust but he doesn't hit like him. Cust was just a better hitter. Even in the minors, DJ only really ever hit enough to make you think you could carry the rest of him in half a season at 25 in AAA and a season at 23 at AA.
This is what a rebuild is though. We're learning things. Some of it is good. I'm really happy in what I've learned about Mullins this year for instance.
Some of it not so good. And as the OP states, from what I've learned about Stewart, I'm pretty much done with him.