If you think sidewalks would benefit an entirely car-based community, I’d wonder if you’ve ever been to suburbs. You’re suggesting building (and maintaining indefinitely) the length of sidewalks, along with road crossing markings, signs, street lights, and all the rest that walkability comes with, to cover a sprawling area where, crucially, people don’t walk, and you are seriously saying that this startup is the money-burner?
Sidewalks will either fall into disrepair and be useless in a few months, or continuously drain the budget just for the benefit of [slow as hell and easy to steal] delivery bots. At this point, one might consider just moving those bots underground, so that they have no obstacles, are harder to steal, can move faster, can handle really large payloads like furniture/boilers/cars, and you have much shorter distances to maintain because they can go direct instead of being limited to public roads. As you can see, perhaps someone has given it a bit more thought than you.
Of course, you might want to consider decent public transit and replanning the entire area more densely, that would lead to useful sidewalks and actually benefit the community (and probably remove the need for these delivery trains), but in the US it’s never going to fly.
The only alternative to underground trains is armoured aerial delivery drones, and I tell you that’s where it’s at. If you don’t do it today, Musk will tomorrow.