All of that said, you might be able to use our Policy-Based Routing capabilities in the controllers to maybe re-direct specific traffic you want to send to your caching appliance while letting non-cached traffic pass on normally. It really kind of depends on your caching server and architecture, etc. Maybe send any HTTP traffic to the caching server but the rest passes out to the default gateway, etc.
I am no web caching/PBR expert though. You might want to engage your local account team to brain-storm ways to accomplish what you need without having to use those proprietary technologies ;)