Let's Just Make Blitzcrank a Heat-Based Champion
Seriously, it's thematic, and it will allow Riot to put drawbacks into his kit that feel better than a slow that just comes off for using his ability. Have his Rocket Grab generate 100% Heat, reduced to 50% if it hits a target so that he still has his combo but he's also heavily punished for missing a grab. If Grabs are too toxic in lane still then just make the duration of the stun/displacement based on rank.
You could also finally give Blitzcrank some bonus for leveling his E, by making the Danger Zone part of his E scale with rank. Here's my suggestions:
While in the Danger Zone, Blitzcrank's Rocket Grab silences enemies grabbed by it for 1 second after the stun. While in the Danger Zone, Blitzcrank's Overdrive gives him 10/20/30/40/50 magic damage on-hit for the duration. While in the Danger Zone, Blitzcrank's Power Fist reduces the target's armor by 5/10/15/20/25% for 2 seconds.
And then you remove the silence on Static Field and replace it with the ability to disrupt channels, like you did with Viktor's Chaos Storm, because a 0.5 second silence is just weird, especially on AOE, and it's really only supposed to stop Nunu and Fiddle from being annoying anyway.
"The magic calls to me"