Arsenal have Holding, Saliba, Gabriel, and Mari ahead of him and are looking to buy Ben White from Brighton. He's 6th choice CB at best, there still might be a path forward for him at Arsenal, but I think it's likely that he is already thinking of making his next permanent move.
I say we go for it, we can offer so much more than any other club in the Championship (except 15k a week salaries).
Ring Arsenal right now, offer 750,000 plus a 35% sell on fee and when we eventually sell him on for 5,000,000+ in two seasons Arsenal will have made a nifty profit and we'll have benefited greatly from his on field performances.
I'm generally skeptical of any new big money signings that aren't proven (Bez and Nuttall wasted Sadler upwards of 500,000), but with Ballard we know we are getting a quality CB who is absolutely already capable of playing in the Championship.
CB isn't the biggest need this transfer window, but when quality becomes available you have to jump at the opportunity, regardless of whether you need it or not.