A suggestion to make Zilean (even) more interesting

I'm really enjoying the Zilean changes, and am glad to see that Riot has decided to buff him since his release (with more buffs incoming according to the PBE).

However, with the loss of the interaction between Rewind and his ult, a lot of Zilean players have been wondering whether it should be replaced with something, and the mechanic be put somewhere else.

In another thread I made the suggestion of them replacing W with an ability that also interacted with his main abilities. However, after thinking about it, I believe there is still a way to make Zilean interesting to play, retain his W as his unique mechanic and at the same time add an interesting and complex champion that fits the complex nature of a Chronomancer.

Suggestion: As Zilean is a combo-mage support, emphasize that combo and its relation to W, in order to create a more nuanced and interesting champion.

Currently Q-W-Q on the same target = a powerful but difficult to land AoE stun.

Make E-W-E on an enemy target (aka you need a certain amount of CDR to pull this off) cause an 'X Marks the Spot' effect Ala Kunkka from Dota 2 that triggers (and damages?) after the player has moved a certain distance from the spot. Fitting for a time mage. Maybe make allies have the ability displace themselves briefly (give them a short ranged blink) with E-W-E

Make a Combination Q-E on the ground, where the bomb is transformed into a fixed AoE zone of control debuff which echos damage done to those within.

Make a Combination Q-E on an enemy target do something different, like make all nearby targets take increased damage from the second bomb.

Make a Combination Q-E on an ally, make them deal more damage based on damage taken or something.

Admittedly a lot of these ideas are possibly crazy strong abilities. Even if the idea of them being gated off with each level in your ult were implemented, I feel like they might be too strong. However, I think that the idea of allowing different combinations that, when combined with W, would make Zilean more interesting to play and/or more useful. And the tradeoff would be, as it always has been, that he would have to expend larger amounts of mana to perform these feats (QWQ vs Tibbers, former Permaslow EWE vs near Permaslow Nasus E).

What do you all think? I'd love to hear other people's ideas on the matter.