I'm someone who's been on the business end of a subpoena for a platform I ran, and narcing on my friends under threat of being held in contempt is perhaps the worst feeling I'm doomed to live with.
"XMPP is ..." not the solution I'd recommend, even with something like OMEMO. Is it on by default? Can you force it to be turned on? The answer to both of those is, as it turns out, "no," which makes it less than useful. (This is notwithstanding several other issues OMEMO has.)