A Champ of Mimicry

I've had an idea for a champ for a while. Basically, it's a mimic. I don't have an exact idea of how it will look (shapeshift? But then I don't know how skins would would work...), but it's skills are pretty simple.

Like Nidalee or Elise, this champ starts with 1 already in ultimate. Similar to Kalista's ult, this champ's Q, W, and E have no use until his/her ultimate is used on an ally or enemy champ. Its role could be literally any position.

ULT: Takes the first three skills (QWE) of either a selected enemy or ally champ. (No Cost. 1 second cooldown).

Q: Blank until ult is used. W: Blank until ult is used. E: Blank until ult is used.

Passive: The Mimic Champ starts with only a health bar. When stealing/borrowing skills from an ally or enemy champ, they will also gain that champ's secondary bar (i.e. mana, energy, etc.) unless that champ has no secondary bar.

So, to sum this up, the champ can swap between the QWE kits of every champ in its current match-up (within range), but has no access to their ultimates.

ALTERNATE ULT: Takes the first three skills (QWE) of either a selected enemy or ally champ. On Enemy Cast: Deals damage to enemy champ. On Ally Cast: Gives a temporary shield to the ally. (No Cost. 120 second cooldown.)

I like the first ult better since it'll allow faster swapping of skills, but this alternate ult gives a better level scaling by allowing the damage done and the shield given to increase as you level up. The damage would scale off AD and the shield would scale off AP.

This champ would require a lot of skill and forethought (what will you build when you can swap between AD and AP kits on the fly?) but could be A LOT of fun.

Of course, I'm sure I'm forgetting something that would make this impossible. Is there a champ out there who requires their ult to function? If so, would that break this champ? But if you think this champ is possible... how would you use it?