In the end, SE's comment to the playerbase was:
We will also be looking in earnest at the possibility of implementing an auction house, as well as continuing to improve the functionality of the item search feature.
I suggest that SE simply poll the playerbase directly, via Lodestone.
Do you want an auction house? Yes or No.
SE can preface this poll with information about why they have avoided implementing an AH. They can wait to poll the playbase until after February improvements to the Ward search system. I personally care very little about this topic, but for others the AH is a make or break issue deciding if they will play/ continue to play FFIXV. In that case, I do care about the AH because I want players to be happy with FFXIV, so it can have a long and healthy future.