Something else for the Aegis, interaction with Supernatural Abilities and non-Hermetic spell casters.
Since Supernatural Abilities have a "Casting Total" and are treated as spells for calculating Penetration, does the Aegis reduce their "Casting Total" by half its level for foreign beings within the Aegis. While for some Supernatural Abilities it might seem silly (Second Sight, Sense Holiness & Unholiness), there are many magic traditions whose "spells" are actually Supernatural Abilities. My own groups interpretation is that it affects all non-"passive sensory" Supernatural Abilities, which means Second Sight and Sense Holiness & Unholiness are generally unaffected (except traditions which require actually casting them like Folk Witches), while Divination is affected. An official answer on if it affects all, some, or no Supernatural Abilities would provide clarity for groups who have not made a group ruling.
Looking at the affect on non-Hermetics the text is very vague, since it specifically talks about applying to Magi casting spells with no clear indication that it even works on non-Hermetic spell casters. While I have always seen it played as applying to non-Hermetics, that is not the way the text is written and is based on assumption. The specific mentions of "Magi casting spells" (along with much of the other text) has been copy/pasted since 3rd Edition. 2nd Edition is actually clearer since it only talks about spells cast by those who did not participate in the Aegis, with no mention of their form of magic.
Finally the effect on the Penetration of Magical Creatures should be clearly stated as affecting their Magic Powers, while any effect on spell and Supernatural Ability use should be brought in line with the final decision on the Aegis effect on said.
While most likely to out there for errata, there might even be an affect on Might beings ability to regenerate Might Points by resting within the Aura based on how the Aegis is defined. For example if it works by forming a barrier which interferes with non-natives ability to draw in fluid vis to work magic with, then it should also affect their ability to recover Might Points by resting in the Aura.