Here are a few other items that should get the same treatment that the got because they'd be so great as costume sets.
I know that not all of these were originally costume trunks, but they are all full outfits with outdated art that would be 5000% more wearable if given the same treatment.
Also, while I know they're part of a series, the Ladies Dancing and Lords A-Leaping would also be good candidates for this treatment.

The Tanto would be wonderful.

Hm. It would be really nice to separate the headpieces from the body pieces, and separate the skirts, dresses, tops, wings and pants. But the site is going to lose money if non-CS costumes are separated into many parts like the CS costume trunks are. Separating them into 2-3 pieces could possibly be okay, but idk how feasible it would be for the site to do it to quite a few old items. Subeta has definitely been known to surprise and spoil us. :x
I wouldn't say no to having some of those items revamped though! And I definitely wouldn't say no to having old one-piece Costume Trunk & Spooky Costume Trunk sets finally getting separated, revamped and added as permastock to the CS.
The Fairytale Panel went and knocked my expectations out of the park, and judging by how happy people were with the release in the news comments, I'd say there's definitely a market for more CS costume trunk items.
I don't see how putting new items that lots of people would want in the Cash Shop is going to make the site lose money?
I don't do Christian imagery but I would really love to have some of the dresses the angels are wearing without the halos and wings, personally, and I really want the Djinn lamp, the Scots formal dress and the Maiko outfit as separate items.

@ Valiska I think we misunderstood eachother. :'D I meant the site would lose money if the items were revamped but were kept out of the Cash Shop.
A lot of the items listed in the first post are not Cash Shop costumes. If Subeta separates & plops those items into the Cash Shop as trunks, you can bet your butt there's gonna be backlash about the hoarders being the lucky ones and getting a leg-up on things. And if Subeta puts only the separated pieces into the Cash Shop (ex. Fallen Angel Costume Wings, Adelita Dress Headpiece, Bell Angel Wings, etc.), I'd also expect people to be a bit salty about suddenly needing to pay for separate parts of costumes when the costumes themselves used to be essentially "free" by virtue of being restockable/Melody Items before they were retired.
Anyway, I'm rambling, but I hope that made a bit more sense. 4 hours of sleep does bad things to the brain.
Though, come to think of it, this is the kind of thing I'd love to have a poll on! It'd be a pretty good way check what the userbase wants & would they be willing to pay for something like this.
The site revamps items all the time, so...? I mean I guess I'm not getting where the cost sink is, because I do not know how much they pay the artists or whether it's per item, per hour, or a "salary" that doesn't change.

A revamp of a wearable is 1 item image revamp with 2 wearable overlay revamps (or only one, if it's not a gender-specific overlay). Turning that item into a costume trunk with 3+ pieces means more images, both for overlays and for the separate items. All those images have to be drawn and paid for. Like you've said, it depends if it's per item, per hour or set income.
iirc they supposedly stopped doing CS costume trunks because it wasn't cost-effective, so that's where I'm drawing my conclusions from. Don't get me wrong, I would like separate costume bits, but I'd kinda also like Subeta to make some dosh. :'D
I totally want them to make money too, I have way too much sunk cost in this site lol (we won't talk about the amount of cws I own plus I'm releasing them now).
But honestly if the artists' pay were dependent on what they made, I am really not sure why there are so many revamps of non-wearable items. I've been puzzled for a long time as to how it helps the site make more money for the cakes in the pet food shop to be prettier. (OK maybe I'm just annoyed because I can no longer tell at a glance which of those items have been eaten by all my pets, as they don't look the same.)
I mean, honestly, items we buy with SP don't make the site money, do they? SP comes from grinding, which means more pageviews and more server load.
I don't know about cost-effectiveness with respect to the costume trunks, but if they didn't make you pick a gender (which, honestly, is dumb, since even if a player only makes avatars of one gender, there are more than two genders and the gender assignments are very arbitrary, particularly once you get into the realm of weapons, backgrounds and companions) and gave you all the items, they could charge like delish sets. At a certain point with delish sets it's more economical to buy the whole thing even if you don't want all of it because the set is less expensive than the number of items you want to buy, and you can sell the rest for SP.
The thing the site could do to make more money is kill the batch limits/"scamming" rule and let people who find that their CWs are more popular than they thought they would be sell as many as people will buy.

Just don't...limit your items if you don't know how popular your items will be? I don't see why an actually useful rule would have to be nuked for this.
Anyway, I think that the SP items should be turned into trunks; we do have items that are trunks gotten via on-site currency and not CSC so that wouldn't be a first. But absolutely no to putting items that were gotten for cheap/free into the Cash Shop