Solution to pink wards late game
+ (any of: 
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Why?
this is the best for ward scanning. So you can't give it more power.
this is counterproductive with sightstone items, so you don't want to penalize players.
this, like oracle, is too strong to buff just by its own merit.- this item is currently the only trinket that is 100% obsolete late game. So why not give it the ability to drop a pink ward late game to encourage people to keep it from time-to-time?
Anyhow, it's just a thought I had. You would be sacrificing better ward-sweeping ability for the ability to have pink wards in hour-long games. Also, as it requires a completed item, it's not like people start getting free wards right away. But the option is there.
items give a bonus slot for pink wards