Can I summon figures into a non-adjacent region?
It's a clever loophole, but I think it is an unintentional one. You've pointed out most of the reasons it's probably not intended to work like that already:


The rule is intended to model the movement of troops from one region to an adjacent region. It doesn't make any thematic sense to summon multiple troops to an adjacent empty region that you used to have a presence in.
What about the round after? And potentially the round after that?
How does this interact with Chaos cards?


The last two points are not defined in the rules at all, which is significant.

Most compellingly, this violates the general game design principle that it's a bad idea to make key decisions pivotal on invisible board states, stored only in player's fallible and biased memories. Once Khorne has moved their Bloodletter, everyone at the table would have to remember that he used to be in Norsca. Potentially they would need to remember this over multiple rounds, if Norsca remained empty. Since this state is not reflected on the board, if there was any dispute about who was where, it can't be resolved by inspection. That's just bad design.