How to combine free non-guaranteed retrieval from IPFS and paid guaranteed retrieval from Filecoin

[stanbar]

Hi, I'm working on a project for anonymous and fair-exchanges between users and service providers. Filecoin is a layer which guarantees that the files were uploaded at a particular time (proof-of-existence) and that they were available for the other party (proof-of-availability). I need those properties mainly in case of a dispute between the user and the service provider. Filecoin deal proves that the content was created and available for the duration of a deal.

From the UX standpoint, it is problematic that users have to pay for the retrieval of files. I understand why, but I would like to avoid it if possible.

I am thinking of a two-layer solution: IPFS (default, free, optimistic) and Filecoin (fallback, paid, guaranteed).

In a normal scenario, the service provider uploads the content to both Filecoin and IPFS.
Then, the user fetches the content from IPFS for free.

In an abnormal scenario, the service provider uploads the content to Filecoin only.
The user tries to fetch the content from IPFS for free but fails. Therefore, he fallback to Filecoin and pays for a retrieval. The service provider is punished by some reputation/punishment mechanism.

Is there a solution that I described?
Is there any other solution which allows for free access to content stored on Filecoin?