There's plently of VPNs that offer unique IPs, or mobile/LTE IPs to connect to, you don't necessarily need to connect to a datacenter or an "abused" residential address.

But there's a potential for a business here: rent small spaces and offer to set up the small boxes for a fee.

These exist. They will scan your physical mail and email it for you too. People who RV all the time use it.

This is interesting and it sounds like you have experience in this area. Can you share specific examples of these services?

I cannot, a coworker who retired to do the RV thing was telling me about it. I think the one he was going to use was in one of the Dakotas