[s1artibartfast]

I'm not saying it a complete solution, but do think it can alleviate some concerns.

>My first question is are people who are willing to use a toilet publicly exposed actually likely to use it vs just some quiet street.

I believe the person willing to take a shit on the sidewalk on busy street, would also be willing to do so in a metal receptacle with TP provided.

I think there are engineering solutions that might not make it unpluggable, but give it a pretty high up time.

You're right that it might take some trial design and study. But that is an argument for trying it!