Appending keys to ngx.req and ngx.resp

Is it a bad idea to append new keys to ngx.req/resp? For example, would the following be considered bad?

if ngx.var.request_method == 'POST' then
  ngx.req.read_body()
  ngx.req.rawBody = ngx.req.get_body_data()
  if ngx.headers['content-type'] == 'application/json' then
    local ok, payload = pcall(cjson.decode, ngx.req.get_body_data())
    if ok then
      ngx.req.body = payload
    end
  end
end

So that I can automatically parse the post body in the instantiation of my app, and then just pass around ngx.req and ngx.resp to all my controllers?

No file or test is identified; begin with the ngx.req and ngx.resp API entry points named in the issue. A complete outcome would need a maintainer decision on whether these extensions are supported and a specified code or documentation target.