Remote Filesystem

Hi, I am a student at an Italian university.
For various reasons we would like to create a collection point for university notes relating to the entire department.
I found your open source solution and judged that it would be perfect for our project. only problem, being a student initiative, we are almost at 0 budget and therefore storage could be a big economic limit. to solve this I thought that multiple free Cloud services could be used together.
Let me explain better, I would like to be able to use GDrive, OneDrive and GitHub as a “remote filesystem”, but giving the possibility to search for files on multiple accounts at the same time.