Assuming you don't want the shuttle to drive through downtown Disney, the only feasible way to have a shuttle is from the front entrance of the pph, and it would somehow have to get to the tram path of the Mickey and friends lot to the esplanade. That trip may take longer than just doing the walk.
I guess you could also go from back of pph to the Mickey and friends lot.
Then of course, you'd either have to go through security check at Mickey and friends lot, or before you boards the shuttle.
When the Disneyland Resort Plan was written and approved by the city of Anaheim in the 1990's, Disney specifically had themselves exempted from using the ART system that was designed by the city to reduce air pollution and amount of vehicles being used as Hotel/Motel Shuttles, and basically required the Lodging locations to use the "Anaheim Resort Transportation" system that is operated by the city through the Anaheim Transportation Network. (The Candy Cane Inn and the Majestic Garden (former Sheraton) got grandfathered and still operate their own shuttles).
There was a proposed route, basically a full circle Route that goes from the Transportation Hub stop south down Harbor, west on Katella, north on Disneyland Drive, a stop at GCH, then continue north on Disneyland Dr to heading west on Magic Way to the DLH Valet, once again a stop, then back going south on Disneyland Drive to the PPH and a stop, then back to the Transportation Hub following the route used earlier. A full circle route, with 4 stops, similar to many other ART Routes. And since it is on city streets, has to be ART and not a Disney Tram like the M&F one.
Ironically Disney had to team up with ART when they opened the Toy Story Lot, and needed Bus service on city streets. (The buses are officially ART Route 20 and operated by ART, not Disney. Disney does use CM's to help guests load and unload at the stops, but on board the buses, everything is an ART employee including the drivers).
The other two 3/4 of a mile Hotels/Motels are the HoJo's (has ART service) and the Candy Cane Inn (has its own shuttle).
As part of the Eastern Gateway project and getting the zoning approval, Disney has offered to work with ART to create a new route for the current Hotels on Harbor between Disney Way and Manchester. Basically starts at the new Transportation Hub on Manchester, south down Manchester/Clementine to Disney Way, a stop near the corner, then west on Disney Way, and North up Harbor with a couple of stops on Harbor. Then a right back onto Manchester, maybe a stop near the Courtyard/HIE, and then back to the new Transportation Hub/Security Check and bridge entrance. Would run every 20 minutes, just like the other nearby ART Routes.
And while officially the DLH is a 1/2 mile property (Front Lobby to the Star), since the Lobby is close (east end of the Fantasy Tower), you can add close to another 1/4 of a mile staying in the Frontier Tower and on the East and West end of it (elevators are in the middle) so close to a 3/4 of a mile walk each way.