A weird Zilean passive

What if he could loan experience?

His current passive gives a small amount of xp increase, that is somehow related to the concept of time gameplay-wise, and is considered not much worthy so i tought to a different, and probably exxagerated system to better reflect the fantasy of experience/time manipulation.

In my idea Zilean once he gets at the shop can purchase some buffs, a bit like Gangplank does for his ult, that gives to him a buff that alters the experience gain. Zilean can get only one active per moment, and is totally not obligatory. One of the buffs allows him to borrow time from the future: he gets enough experience to level up ( without considering experience already gained ), but leveling up for the next two levels takes more ( so the actual level he gets is normal but the following 2 take more, i was thinking about 20% and 40% more respectively); this could allow him to get a imprevedible power spike, getting an edge in an incoming battle or allowing him to be a stronger lane bully at the price of later levels. Else he is able to lend time: he denies the amount of xp necessary to level up, but once that expires he gain a massive increase on experience gain and experience per second, up to a percentage of the denied experience ( i was thinking about 150%). This allows him to trade power in a more safe moment, so he can get the upper hand later on.

These ideas do not allow him to be better in a precise role, so it can be more focused on deciding how to spend that power shift. I tought about letting him be able to get other buffs, spell empowerements or just gold, but in the end it felt weird to have to trade power for another kind of power. Also this passive should not be an huge power budget: everything is a double-edge, and the Zilean player could even not bother with this if he decides so.

Any toughts?