Using RapidJSON instead of the existing JSON-like data structure would make having both server and client-side rendering easier. Basically, you'd pass the JSON data to mstch for rendering if a prerendered page is needed. And, RapidJSON would generate the JSON string when the browser makes an ajax request (for client side rendering). No need to have separate code to assemble the data for the different uses.
Alternatively, a JSON parser and serializer that uses the same data structure as mstch would work too (preferably without external dependencies like Boost).
Using RapidJSON instead of the existing JSON-like data structure would make having both server and client-side rendering easier. Basically, you'd pass the JSON data to mstch for rendering if a prerendered page is needed. And, RapidJSON would generate the JSON string when the browser makes an ajax request (for client side rendering). No need to have separate code to assemble the data for the different uses.
Alternatively, a JSON parser and serializer that uses the same data structure as mstch would work too (preferably without external dependencies like Boost).