Champion Concept: Pyco the Mimic

This is just an idea I had in the middle of the night, and I wanted suggestions from other players how they think this might work. All discussion is completely hypothetical.

Pyco, pronounced pico, is a champion that uses other champions abilities for herself.

Abilities

Q -> Replicate: Pyco steals an enemy's ability and can use it as if it were her own. This skill persists until she casts Absorb (w).

W -> Absorb: Pyco absorbs a stolen power and gains a buff, shield, or heal.

E -> Enhance: Pyco gains AP equal to a % of her bonus AD, and gains bonus AD equal to a % of her AP for x duration.

R -> Identity Theft: Pyco copies an enemy champions ultimate and stores it for x seconds. If pyco doesn't use this ability the cooldown is halved. This ability's cooldown is static and does not change based on the stolen power.

Passive -> I don't know. Input?

Explanation

Q: The stolen power can on be another champion's Q/W/E and the scaling remains the same which means she can be built as AD or AP, but this skill can be changed any time. Choosing between Q/W/E can be similar to Twisted Fate's card pick and the stolen ability's level is based on the level of her Q.

W: I thought this might be a long CD heal (20s?) that prevents changing abilities too often, but rewards players that do. Alternatively it could be a shield or another buff.

E: This ability is a medium duration buff (8s?) that allows Pyco to take on a hybrid role so that if she takes a different scaling ability than her build some use can be made of it in bursts. Percentage bonus can increase per level. 30%/35%/40%/45%/50% or something similar.

R: This ability would have it's own cooldown so it can't be used to steal a Corki rocket and be immediately used again. The stolen ultimate would need to be used within a set time to prevent sitting on it, but would refund some time on the cooldown if unused. It needs to be an enemy ultimate to create counter player, and to prevent easy setups with teammates. Possible to still use teammates ultimates.

Passive: I have no clue what kind of passive would fit well in a champion build like this.

Complications

Animations alone make this impossible.

Resource usage? Mana, Energy, None, Rage? Should it change based on stolen ability, but make W and E free cost?

Plenty of others I'm certain.

P.S. Yes, Pyco is an anagram for Copy and yes she would be a yordle wizard.