I'm not sure if I understand what you're suggesting. As I understand it, the argument isn't that Walmart is literally getting subsidies. It's just that Walmart employees are getting welfare, so Walmart doesn't have to pay to support them, reducing Walmart's costs hypothetically compared to an equivalent company which paid their workers a better wage.

So if you created a company which provided as good of working conditions as possible, your employees wouldn't need welfare, so you wouldn't be benefiting from the "subsidies". Also, your costs would go up, so you'd be more likely to go out of business than Walmart.