I have one doubt,
I am not sure this feature already supported by openwrt.
I want to setup a content caching access point,
for example if user1 accesses a internet resource e.g. http://www.test.com/test.html
then that resource is saved in cache(or attached disk drive) and served to user1
now when user2 tries to access the same resource http://www.test.com/test.html
it is served from cache instead of again downloading from internet.
It is not entirely impossible, but the sum of requirements, drawbacks and wasted efforts makes the whole affair pointless in most cases.
Major blockers are SSL, dynamic content, IO-performance and storage capacity.
Nowadays web content caching mostly relies on web browsers and CDNs.