you can't create different response depending who is making the request.
Also, the CSS does not care if a server does a dns request. It will answer just like for any other devices.
However, it will respond with its VIP and when the server opens a webpage to the vip, the request will be loadbalanced and therefore there is no guarantee that the response will go back to your server.
Moreover, if servers can open connection with the vip, you need client nat to guarantee that the response will not go from one server to the other but instead go first to the CSS.
As you can see there is precautions to take for what you want to do and I think that the solution you have in place is the easiest to implement.
Regards,
Gilles.