It is possible to put them in other places, there's enough space for it, but it should be done with solid flagstones, and not paving-blocks. Sidewalks and no-parking poles were not a 13th century feature of today's Rue Sauval. Sidewalks are especially necessary on the big roads that approach the capital. In bad weather the paths beside these roads are unusable. If one walks in the road one risks getting flattened - therefore one has to walk in filthy and slippery mud.
People carrying heavy loads can fall and injure themselves.
Above all, the worst is certainly the deadly wall that dominates everything from the Saint-Denis barrier to La Chapelle. All the panniers of foodstuffs arrive by this way. Several women have broken arms and legs there. It happens all too often. The religious community of Saint-Lazare should, at their cost, make a good sidewalk along this wall.