I don't think Gibson cares about maximising profits. He cares about minimising losses so a retail outlet that sells all its stock is seen as a success. He might be a great businessman in the domain of hauling bulk but he's definitely not a retailing guru.
I find it baffling that anyone would ever assume the club knows best and they have superior knowledge to anyone passing comment. Away from the footballing side of things the football club is actually a tiny business, and it pays peanuts, so the chances they have the best procurement, stock modelling or data analysis is slim. The chances that there is someone on here that knows more about retail than Gibson and his retail team is pretty high. There are lots of people with experience of working in senior positions in companies that know how things work, there are even more people that have been in shops a million times in their life and understand that a model based around 2 products that are never in stock isn't being run as efficiently as it could be.
I don't think there is any point asking the club anything. They don't care. I can't imagine Gibson is particularly flexible and if he's happy with being told that the stock is all sold, at full price, and there have been very few returns then it's probably not worth risking his wrath by telling him that there are better ways to do things.