Payload free package tied to an enrollment (or other relevant) trigger with that command as a postinstall sscript

A better question might be why you want the content caching activated on client devices? Are these clients distributed? If they are, then caching content for one device isn't all that effective. If they are all in one location, then you could potentially be utilizing resources of client devices as they serve content to peers. You'd be better served by having dedicated content caching devices distributed on your network.

Just my $0.02

I understand you ask @jcarr :)
I work for a mobility services company and I could have to set up maybe hundred caching servers for hundred schools.
I am looking for how to do it as quick and as easily as possible.