I think one of the main reasons sites like the Divine Lorraine aren't included in walking tours is its distance from blockbuster stops like Independence Mall, not to mention the racist and classist stereotype of the neighborhood as """dangerous""" that tourists might be reluctant to visit.
How would you plan out a walking tour that covered a wide enough geographic area, and got people out of "tourist areas," in order to recount a more comprehensive and recent history of Philadelphia? Would you partner with an organization that would just offer multiple themed walking tours in different areas? Or would you consider if a bus tour would be more appropriate? (Though that might be more costly...)
Have you talked with @johnesmithiii? I bet there's a lot of room for collaboration with his Philly History Truck plans...
Can't wait to see where you're going with this!
I think the vast majority of tourists will always go to the blockbuster stops, partially because they see the national narrative as more relevant to them. Even the art museum is too far away for them to see on walking tours--the tourists I've interacted with are always interested in it until I tell them where it is and how hard it is to get there on public transit (it's really a shame the subway under the parkway was never built).
However, I doubt it would be too hard to get schools to visit local sites, especially because many of the kids live nearby. 75 minutes is about the longest most of my school groups last before they're bored and tired of walking, so the geography still presents a problem. Ideally whoever develops the first tour, if it's successful, can then develop more tours in different areas. Buses are too expensive, and I think you get a much better experience of the neighborhood on foot.