Fire Blast
First of all, best of luck to both of the concepts. After a little convincing, I now believe both to be interesting concepts, that help us explore either the effect of a varying movepool or the psychological effect of a threatening reserve pokemon.
Overall, I feel like Korski's Sketch Artist is a weaker idea. As I have said before, it would be hard to make a pokemon who can take advantage of most of the interesting, but less-seen moves without making it broken. I mean, look at Mew. It has a massive defensive and offensive movepool, and straight 100s. 100s are great defensive stats and ok offensive ones. So to make something that can take advantage of an opportunity like this, we have to base it on some existing pokes in similar situations. And I feel like if we just make Mew with a better typing and stats more directed towards the "jack-of-all-trades" goal, we will have a broken pokemon. And all we would learn from that is that we can in fact make something too good with the tiniest concept.
On the other hand, it would be easy to try and stray from something balanced, in which case we'll either make something ineffective or something useful but that only really takes advantage of one or two sets. If anything, it will be interesting to see if we can walk the fine line between these two. If we can, that really tells us something about CAP and what we can do.
With Fire Blast's Theoretical Threat, I feel like we can make something that has a balanced product more easily, as well as a product that fits the concept. That being said, the goal of the CAP isn't just the end product, it is the process. With Theoretical Threat, I believe CAP would have the look into psycho-analysis more, which is something that CAP really hasn't done. I think both the end product and the process for this are something to observe. Since everything about this makes it an interesting experiment, that's why it gets my vote.