This sounds really cool and I'd be interested! I'd vote post Mage Storms as well, and I like the idea of Herald trainees NPCing their own Companion, since otherwise you'd end up with some people having extremely limited CR if they're playing a Companion, and lots of multi player action threads (which slow things down a lot.) Maybe acceptance emails for Heralds could include a quick personality summary for their Companion, or something like that?