What if there was a champion that can "steal" untargetability?

What about a champion that can "steal" untargetability? It can apply a mark on a champion and when they use untargetability while the mark is active, the spell goes through, but it is automatically copied by the champion. To avoid confusing visuals, you could just apply a silhouette of the champion using the untargetability as a particle on the champion that stole it. Like, if you're copying Fizz's untargetability, imagine a watery silhouette on Fizz using troll-pole super-imposed on the champion. Hooray for readability!

What do you guys think?

The champion would be able to move around and use their own spells while their stolen untargetability is active, making the champion an extremely potent counter pick to Vlad, Fizz, Lissandra, etc. who cannot use their spells while their untargetability is active (unless you count Fizz's wide, large AoE damage at the end.) It would also copy Zhonya's but without a "stolen silhouette" particle, instead the champion turns gold but can still move and cast (imagine how cool that would look.)