No always online would be worse than no used games.who cares about used games,online only is worse easily. there will be a time when used games are no more anyways.
You will need to validate a code before install - requiring an internet connection. No Internet connection, no install, no install, no play. Beyond that 'always on' has no significance to offline play.
If that's the concern, I think we can all calm down. Any other model is unnecessary burden on resources. A more draconian approach would be to require a heartbeat style check-in. More secure yes, but in a closed system like a console, absolute overkill. You can always add additional piracy checks during actual online games and live updates. I'll be shocked if there is any other method to doing this.
Used games are big deal. It's a big market, you don't get to shut down a trade and not hear about it.