I just realized that it made a lot of sense for them to make Elrond and Galadriel allies that leave play at the end of the round: if they didn't, they'd stick around long enough to receive and make good use of the attachments meant for their hero counterparts, since the attachments only specify the character's name and not that it should go on a hero. Specifically, I think Vilya and Mirror of Galadriel would be really strong for ally attachments.
The fact that OHUH Gandalf is relatively "under-played" and that he has a significant disadvantage for remaining in play meant that they felt leaving Gandalf's toys available for the allies was OK.
Another example that I believe someone else brought up before was that Leadership Hero Faramir has an a ability that would make ally Faramir extremely powerful, so they made sure it was on a card with the same name so that it could not legally target ally Faramir.
Any other examples of good work by the designers done in these somewhat stealthy ways?