New xp mastery

I remember in season 7 when you could buy and make your own runes. The creativity and possibilities in it were amazing but not necessarily useful. I remember however that there was a run you could get for xp gain. It could put champions who had their powerspike at higher levels at that point slightly faster without really being overpowered. I was wondering if you could add a rune to the inspiration tree that could increase xp gain from different sources at different rates that would be fit toward separate roles. This rune could change the strategies of the early game for mid to late game champs and would not really change the effectiveness of early game champs.