I've discussed with Jake about adding a concert size, given that he did all of the Compass Rose ukes when he worked for Rick. Coming from a guitar background, he personally prefers a more like guitar-like sound and that is not easily achieved in anything smaller than a tenor.
Jake has honed his tenor designs over the years. He is absolutely meticulous in his work and some of his design elements are more labor intensive than most other builders. To wit, look at his headstock. It's incredibly elegant. It also takes a lot of time.
He routinely maintains a 12+ month backlog of orders. He simply does not have the spare time to develop another size that mets his own high standards in terms of tone. Maybe he will one day, but for the time being demands for his existing tenor designs remains strong.