Idea for another Ryze rework (teleporting to turrets)

Since riot really wants to keep the teleport part in his kit I was thinking. How about rework his ult like this:

#R - Realm Warp

• Unique Passive: Ryze can teleport to a friendly tower or a fallen tower that he has marked. By rightclicking the tower (or rightclicking the fallen tower to mark). Ryze can teleport to it. Depending on the rank it goes on a 200 / 140 / 80 seconds static cooldown.
• Unique Active: Ryze creates a circle of energy on the ground that slows enemy champions and marks them with Spell Flux. During this time Ryze gains a shield based on his current mana. [180 / 160 / 140 seconds cooldown]

##Extra

When it's to strong a system can be made so Ryze only can teleport to a turret ones. Turrets where he already teleported to are marked only visible to him (similar to talon parcour)