From an informed source (in response to my earlier query):

1. “The problem for the voter in the first scenario is that the ballot may not contain the issues on which the voter is now eligible to vote. The ballot envelope is clearly marked using postal verbiage that the ballot is NOT to be forwarded and the internal post office is not doing thevoter a favor by forwarding the ballot.”

   (Note: still not clear whether they are breaking the law.)

2. ” Under number two, there are multiple issues. If the son or daughter is temporarily away from home — at school, on an overseas trip, mission activity, or on a temporary job — the voter would be better served if we were provided with an absentee address. At any rate, the ballot he or she receives would be correct as long as the home address is the voter’s residence for voting purposes. On the other hand, if the son or daughter now “lives” somewhere else, he or she should vote a ballot with issuesbased on the new residence and should re-register to vote.”
3. Interesting, Oregon only twist: “Double majority issues could also play into these scenarios and if residence challenges were presented, we would have to look into them.”