I think supermarkets are, by their very name, what the markets were. Everything we want can be gotten, mostly. As more families require 2 incomes the days of shopping 9-3 4 days a week are gone, especially once commuting and parental duties are included. You say they need to give us what we want, but what we want is someone with good quality priced well that we can access, even if a market stall meets 1 and 2 it can never compete on 3 when most of us are at work when they are open. I am lucky enough to work near the market but rarely spend money with anyone other than John near Wilkos entrance. I can get it all elsewhere, often cheaper.
What I'd like to see is some street food. A one day street food event, fill the empty stalls with people offering cheap food to eat on a lunch break spent avoiding the office. Advertised well I think you'd get a good turnout, it beats a boots meal deal. I've had food from the market square Wednesday market twice now, I'm sure we could support a few regular traders. That said I've heard mention of a Caribbean food place in there, but I've never seen it?