Zoe W nerf/balance?

What if Zoe could only get balloons from cannon minions?

I think this would window her power a bit more reasonably. As is, her W drops can be a little inconsistent. Sometimes she won't get one for several waves, and sometimes she'll get them back to back. If she could only get them from cannon minions, her opponents would have a clearer idea of when to play around that type of thing.

Plus, with her only being able to hold onto a spell for 60 seconds, it would make her use of those spells require more thought and meaningful use. For instance, she can't just use her blue smite shard on a balloon minion to "re-roll" her summoner spell, and she would be less likely to just protobelt the wave or exhaust you for no reason if she didn't know she had another spell coming right away.

This is just one idea I had to help balance Zoe's W, let me know what you think.