Andy from SatoshiPay here. Am a bit late to the party…
We have also played with the idea, but it’s not as easy as that. You would need to run your own IPFS nodes to pin your data, otherwise it might not last very long on the network. Those operational costs would need to be covered in some way.
The next best thing to hope for right now is probably when we roll out SEP-7 delegated signing support in Solar, so someone can build a web service that does what you want and you can use an account in your wallet to login to the service and sign data.