If you pre-slice the pizza before wrapping, people should be able to re-heat individual slices.
As far as frozen pizza goes, the big guys use special freezing equipment to freeze the pizzas quickly and minimize damage. They also use additives, and, from what I understand, special cheese. Major food science is involved and the end result is barely edible. Without the equipment and the chemistry, I don't think you stand a chance. Sorry.
The biggest barrier is the cheese. Bread freezes nicely- but cheese, not so much. Bake up a pizza and, freeze it and then see how well it reheats. That will tell you exactly what kind of product you'll be selling.
Does this supermarket sell freshly prepared pizza? I went to my local grocer last night and saw about 5 people walking out with pies. Supermarkets have a lot of foot traffic and it gives people the opportunity for one stop shopping. If you've got a connection with a supermarket owner, that's what I'd try to sell them on. Even if there wasn't the space inside the store, perhaps they'd let you set up a stand outside- for a cut of the profits.