Hi Chris, This just sounds like offline apps - such as those using SMP or HCPms.
You don't need multiple frontend servers to run offline.
You just write your app as an offline app, with certain trigger points that synch to the backend when network connection is available. The caching in this scenario happens on the device, and the offline apps run entirely on the device.
There's a openSAP course on this you may find helpful to understand key concepts and how it works... Developing Mobile Apps with SAP HANA Cloud Platform - Jeff Gebo and Dhimant Patel
There's no need to run a front end server locally that I can see to support the scenario you describe. You simply need a frontend server to manage online behaviour and synching when online. I agree with others... consider Akamai Contents Distribution Network to assist with that.
Rgds,
Jocelyn