This is brilliant, I hope that you will open source this to allow anyone to host their own version of this API.
Additionally, it would be great to have some documentation around this implementation even to just reiterate the Steem docs as they can be a bit confusing sometimes.
So, semantically you wouldn't really be "hosting an API" -- this more of a translation layer. But definitely plan on open sourcing it after I get some feedback and formalize the design, as my long term goal is to get everyone moved over to a format like this.
In regards to the documentation, its an interesting point. I actually find the steem api documentation here decent, and I find it quite intuitive to map the "Query Parameters JSON" to the REST format that I'm using. If you try it, it seems natural; for example
{"author": "", "permlink": ""}maps to?author=""&permlink=""