Well, I would never use the peacekeeper outside of a hoffman crew, and I´m utterly unimpressed with Ryle, he is completly useless most of the time againts neverborn with his mighty wp of 2 against all irresistible junk that comes flying at you and I´m yet to see him actually do more than 1 damage with his gun, although I mostly play ressers so I never get a straight flip. I would consider taking Ryle in a Lucius crew but mostly for his melee abilities since thats one thing Lucius lacks, yes he can take the guild guard captain but he is even worse than Ryle. But don't take this as gospel, I seem to have a beef with every guild model above 7 points and I usually don't get anything usefull out of them that couldn't be handeled by 2 witchling stalkers or 3 dogs.
Watcher, Witchling Stalker and Guild Hounds are what shows up in more lists than anything else.