I’ve built CCG with caching enabled for a project that uses remote HTML templates, no big changes needed. I mostly referred to rocketbeans fork with the changes, but can double check if I made any further modifications if you are going to build your own.
As always I recommend that anyone that is comfortable with building CCG on their own check the forks listing I maintain if they are looking for features that haven’t been PR’d to the main repos of CCG2.3 or NRK 2.1, there’s usually plenty of interesting things to find there.
But on to Didi’s point, this needs to be implemented carefully on the remote side (what to cache and for how long etc) and probably isn’t what most users want. Service workers are also an option for this on an individual template basis. If the template is always running it’s easy to not update data or images if updated content can’t be downloaded (simply by checking if the RSS is empty and updating images in placeholder img elements and only moving them to the displayed img elements if they successfully load.