Actually, if Vergeben is aware of "at least half a dozen more" characters, I'm going to try and figure this out.
We know Vergeben has 3 source:
Source 1: Ken image source. Ken theory connects Vergeben to: Ken, Incineroar, Isabelle and Simon, which covers 4 of the half dozen (as his statement was after E3).
Sources 2 and 3 we don't know about, but they would have to have connections to Minecraft and Square Enix. As they know the concepts of the characters, they likely aren't playtesters and may be further inside.
We know Vergeben has 3 source:
Source 1: Ken image source. Ken theory connects Vergeben to: Ken, Incineroar, Isabelle and Simon, which covers 4 of the half dozen (as his statement was after E3).
Sources 2 and 3 we don't know about, but they would have to have connections to Minecraft and Square Enix. As they know the concepts of the characters, they likely aren't playtesters and may be further inside.