the reason why mages wont get active items....
is because then they get late game outplay potential and it invalidates other late game ADCs.
you cant have an edge of night active, you cant have a QSS.
AP champions are designed for early-mid game, (except you veigar)
if you start giving them actives they're going to wonder why the stats are crap, if you actually make it comparable to a morello or a void staff in terms of power then you're now left with everyone playing AP champions simply because they can do more than someone else.
its not that an item cant be thought up. its that riot doesn't want such items around because of the implications it has on other lanes as well. not that it wouldn't help you achieve your goals or give you more to do, but that it would end up just pushing other champions like darius, skarner, or xin out.
that build into something
cost 3800 gold
has no active until you get a complete
at 2900 gold
who are designed to HARDERCOUNTER that STILL get wrecked because of lethality.
I think these are good examples of Late Game APCs/Mages.
defensive? I've killed plenty of people with it offensively as part of my combo