Just pointing out that the original Wiki entry says use of lyrium potions for mages decrease the effectiveness of lyrium, so they'd end up taking more and more over time, and that it causes physical mutation in Mages. Not my opinion, straight from Dragon Age Wiki. What you do in game is up to you, but asking for implementation of lyrium addiction effects more than Cullen, and Cassandra, ...all the Mage NPCs would be effected.
I would be interested in if the addiction caused issues for Cullen at Redcliffe, but I'll have to rely on youtube for that info...since I'd never send Cullen on that mission, nor Leliana for that matter...sorry Josephine is being sent to warn the King of Nevarra instead...tactically a better move, though she may also end up captured...we don't know much more than one of the 3 advisors may be captured depending on your decision.