IP Reward Quests
As a replacement for "First Win of the Day", give each player a "Dailies" Tab.
Every day, you get one quest to complete (you can store up to 3).
Quests can be both general (Deal X damage in one Victory) or champion specific (only on champions you own. Land 10 Rocket Grabs in one victory).
The IP reward would scale directly with the difficulty of the quest.
Simple quests like "Win 5 games" or "Score 10 kills across multiple victories" would give around 500 IP.
Difficult quests like "Get a Pentakill" or "Catch the entire enemy team in Command: Shockwave" would give around 2000.
They could even be map specific to encourage people to play Treeline.
If a quest is too hard for you, you can get rid of it once your queue is full.
Dead by Daylight style.