Tech question - Is the LoL code base to a point now where it would be possible to create a champion that copies other champions' abilities? i.e. A nearby Ezreal presses Q, then this champion could press Q and steal Mystic Shot as for its Q ability? I was honestly hoping this was what Zac would be.

Jordan Willis
The short answer is not really.
The long answer is the tech has always been there, strictly speaking, but the tech to do it easily does not exist.
Skills in league exist as a number of files; the logic of skills lives (mostly) in .LUA files and the numbers live (mostly) in .INI files. If it was as simple as every spell being a single lua and a single ini file we could conceivably do spell replication. Unfortunately it's not as easy as this. Spells often rely on a many additional files--buffs and extra spells. Even if we made it so all the "related" files got referenced along, there's still the problem that every champion has something called a "CharScript". This is a lua file that usually does a bunch of book keeping for the overall character. Sometimes this includes spell logic, sometimes this includes tracking variables that spells need (almost all spells that have an aspect that scales with *character level* rather than *spell rank* will do adjustments for champ level in here for instance).
But let's skip tech completely. Design-wise it's not clear to me that this would make a lot of sense or being very maintainable. What would happen if you stole, say, Azir's Q but had no way of spawning soldiers? What if you stole one of Rengar's skills but had no rage mechanic yourself? What if you're a mana user and steal an energy based spell?
And even if we could find good answers for all of the above, there's the balance level. Many spells are okay only because of their CONTEXT. Champions have an overall power budget that includes their 5 spells and their base stats; taking a spell out of that context could potentially make it unbalanceable.
It seems like a really cool mechanic, but my personal suspicion is that it sounds much cooler than it would turn out to be once we're done balancing it.