I apologize in advance that I'm not actually sure how viable this is from a coding perspective, but even if it's not, it may give one of the coders some inspiration for a solution that does work! Here goes:

Combine the existing Queuing system with a cross between "wishlist search" feature (user shops) and "account search". The way this could hopefully be set up is to have a wishlist search button inside of each user's wishlist. If you pressed the button to be shown only items you own from that wishlist, the request would be entered into the Queuing system. Your request might take a few minutes depending on where you are in the queue and how large the user's wishlist is. You would be notified and provided a link when it finished. Maybe to cut down further on inquiries, all of the permanent collections could be omitted completely (aka only show you owned giftable items). If necessary this feature could probably even be limited to one request every few minutes (especially during times like Luminaire when a larger amount of people would be trying to use it at once).

Why I think this might work:

Before the latest server move I noticed that there were certain sets of activities that would reliably trigger a 504, lag, white pages, or some combination thereof. One of these activities was moving large quantities of items (100+) between two shops. Since we do not have our other shops in the dropdown on the Edit Shop page, this normally involves moving the items to your inventory first and then quickstocking to the other shop. However, I noticed that there seemed to be one very simple way to bypass the errors and accompanying lag to make them almost never happen. This was to move the items from shop to vault first, and then from vault to the desired shop. I believe the reason this worked was the Queuing system that is in place within vaults, which seems to balance the server load over time rather than trying to force it through all at once. If the issue with this wishlist feature in the past was the sudden huge request(s), perhaps the Queuing system could help funnel it through in more manageable amounts.

That would be nice to have, or a feature that trims down your wishlist category when it finds the item in your account. A text only option would be a bonus, to avoid loading tons of images.

Oh man, that's a great idea!