When we signed Holding, he was already 21. Ballard is already as experienced at the same age and even has a promotion under his belt as well as international caps against stellar opponents. I'd consider Ballard to have a higher ceiling than Holding.Ballard is a decent prospect but I don't think he's really someone to consider for Arsenal. We talk about Holding not being good enough for more than a back-up role for Arsenal, and think where Holding was at 19, 2 years younger than Ballard is now.
I don't think we need to really think about people like Ballard in terms of first-team setup at Arsenal, the idea is to get as much profit from him. Monlouis and Awe (and Rekik, probably?) are the guys with first-team potential if things go right.
That said, I think viewing Ballard as a potential sellable asset isn't a bad thing - just that I think we have to be very careful about that. Better prospect than given credit and has defied expectation regularly.