"88.7 Upgrade cards that have a faction icon can only be equipped
in armies of that faction"
Based on that, Kari's elf buddies can equip upgrades that are restricted to the human faction but not ones restricted to elves, correct?
I get that it's entirely possible that when the elves drop that rules get added to specifically to deal with units being used outside of their own faction's armies but this seems to give clear clear direction on how to handle it.