Who has written him off?
Not sure there's a big-league role at present. Would you bench Happ or Seiya to play him? Shaw? If not, where's his role? Given his "dim" baserunning blunders, he's not better than Dean at Dean's role.
Let him play at Iowa, and see if he can improve and sustain as a hitter. Combine power with improved contact, and get better. He's recently gotten hot and gotten his average up to .250. Can he sustain a little bit? If/when injury necessitates a platoon outfielder, he needs to blast through whatever window of opportunity he gets.
Kinda think he's best getting semi-regular AB's, and may need to wait for an opportunity where he either keeps getting them in AAA, or has a big-league chance. Again, if/when he gets that, he'll probably need to do some hitting right away to sustain/extend such chance. 26th-man role might not be his best fit.
But yeah, I'm thinking there is still developmental ceiling for him, and he's better served hitting regularly at Iowa than 26th-manning for Cubs.
Likewise I think he's more likely to build trade value improving at Iowa compared to 26th-manning for Cubs.