In expense of slowing down your ability to store and access data, plus you need a full node to get grants on each device which should access your data.
You just missing the main advantage of the access grant - it contains all needed permissions, they are not stored anywhere, so the only point of failure is you 
- if you share it with someone, they will have the same access incapsulated to the access grant, include derived encryption key. The access grant is a macaroon, a selfcontained cookie, some kind of token. It doesn’t need to be stored on the satellite, it should be stored on your device, which need to have an access to your data.
And storing it on the public blockchain doesn’t make sense - anyone can download your access grant and will have an access. Thus this access grant should be encrypted or you should not use a public blockchain. So you need some controlling server who would at least decrypt encrypted access grant downloaded from the blockchain and then will download data from Storj DCS for the user. In this case why to bother with a blockchain at all? If you delegate decryption to to client, who will stop them to decrypt the access grant and have an access for free?
That’s another feature, and you may implement it right now - you need to write a smart contract contained the access grant and it will control this level of access, like number of watches and so on.
The access grant allows you to specify only read, write, delete, list operations and time before and time after, also paths (buckets, prefixes, objects keys (names)), satellite address, derived API key and derived encryption key. So you need to implement an extension of access grants on your site to control such kind of access like number of watches. And in this case I do not see why you need to use a blockchain for that, only to collect revenue maybe? However it’s a very specific usecase, not generic.