And how do you lure the right stores in, assuming you can decide what the right ones are in the first place? Jane Jacobs doubtless has some answers, but this [is] France. If you give the Parisian city government a slush fund to subsidise interesting shops opening on the Champs Elysees, hey, guess what, the mayor's best friend's brother-in-law has just decided to go into the bespoke millinery business.
My general point is that, for as long as the French think they can suspend the laws of economics in a 400-mile mile radius around Clermont-Ferrand, we should delight in any weird policies they may attempt (eg, declaring yoghurt a strategic industry; imposing a 35 hour week and then regretting it). Just to see what happens.
Actually, Jane Jacobs would recommend intervention in this case. She claimed that neighborhoods tend naturally to become specialized and homogeneous, and so government should zone for diversity. That's about the only idea of hers I don't like. How is the government's definition of diversity better than that of the neighbors who live there? And why should we expect the government to more effectively, ie efficiently, achieve diversity?