File sharing server through mobile hotspot

Create an app that can create a secure space on it's drive to save files, then connect to it's hotspot ability to create a shared drive that others can connect to. Just like having a file-sharing server on a company or personal network, why not have the abiity to do something similar over a mobile hotspot?

This would not only allow people to easily transfer files between their cell phones and their other devices, but it could also allow for sharing of documents between individuals.

Also, it could allow old smart phones to be turned into file-sharing servers.

This idea might need changes to the core system because of securing and manipulating file space, but I'm not sure.