You can use eCryptfs and IPFS for this, there is no need to reinvent the wheel. All you need to do is periodically add the source directory to IPFS.
If you're handling large folders you can't store, it would be trivial to write a script that uses
ipfs object patch to update the source directory on IPFS without storing the entire directory. You can then publish this to an IPNS key.
For access control you can either simply distribute the keys to multiple people (read-only: only encryption key, read and write: both keys), or you could write some simple script for access control however you want it.
Why can't you just use the VPS for storage?
What do you need a blockchain for?
You can mount IPFS directories locally with
ipfs mount. All the other protocols mentioned on that site have FUSE implementations as well, so I really don't see what that brings to the table.
Doesn't amazon AWS give bargain prices on transfer to/from S3?
IPFS is better for running websites due to deduplication and performance. Why pay for storage when you can use your own computer? For the price of cloud storage for a few months, you could buy an old computer from craigslist. It will cost you less and you can use it for more than storage, as well as giving you actual physical control.