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=""