I'm happy to be creative and find some way to use the Storage Space instead of the Application Node Disk Space via some published REST API, but maybe it's easier to explore the options of increasing the Application Node Disk Space.
Do you use the Mendix Cloud? In that case you could request (via a ticket) to buy some extra or move some space such that you have more Application Node Disk Space available. Check in the Metics to see if and when you will reach the limit:
Do you use On Premises or Private Cloud? Then ask your infrastructure team to increase the storage on the application node.
If you really want to make a work-around, you could develop a Published REST API, serving the files. If the folder structure is quite flat, this isn't that difficult. And optionally you can store the files zipped and unzip them on request. Suggestion for setup: