In the new wardrobe we have the option to toggle the avatar's limbs, in order to wear some body mod items, unfortunately most pants and hip zone items have a tiny little unfilled spot where the thumb is meant to be.

I assume that in the future, items will probably be drawn without the hand shape, as some items have already been drawn that way! Like the set, if you'll notice the fabric actually goes over the thumb. And perhaps older wearables would be revamped to fill the gap, but that would take a long time.
In the meantime, I propose a tiny wearable that fills in the shape left by the thumb, and it will be similar to the "basic flats" kind of item where it will be available in many colors - perhaps just a set of one of each color of the rainbow to begin with. The item itself could be a picture of a thumbs-up and could be called "(color) Thumb" with the thumb in the color, so like a play on words like "Green Thumb". edited in alternate idea:
We can call them (flavor) Jack Horner Pies and also make them edible.
Little Jack Horner, that could also work. For this I'm imagining the item art being a pie with a little hole in the center to reveal the inner color, and the description alluding to the avatar having stuck their thumb in it. :D
This way, people who need it can use it and people who don't can skip it. In the avatar example I used above, I would add a black thumb filler underneath the shorts to make the gap less obvious.
Full support.
We can call them (flavor) Jack Horner Pies and also make them edible.
If you want your left hand's thumb to be in front of you instead of looking like you might be scratching your butt/catching-up a bunching or slipping of your underwear with your thumb, you can wear one of those sheer gloves.
The lemma of this is that the sheer gloves should come in the fashion base colors in addition to the usual RL base colors. There's probably no good fix for all of the Curious Dolls.
Full support
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Little Jack Horner, that could also work. For this I'm imagining the item art being a pie with a little hole in the center to reveal the inner color, and the description alluding to the avatar having stuck their thumb in it. :D
Full support! I'm trying to make some bottoms and body mods right now, and struggling to figure out if I should fill in the thumb area or leave it blank. Having a thumb-shaped basic wearable would help SOOO much! There could be a thousand colors, but even just the original 28 skin tones in the wardrobe would be amazing and helpful.
Sorry for the off-topic ping, but many of you would probably be interested in seeing this implemented.
It doesn't actually appear that way anywhere except previews and in the wardrobe. It's appropriately positioned outside of the wardrobe functions - it was brought up to staff and confirmed it's not supposed to appear that way and is an error. I didn't even see it doing that earlier when I was making an HA, it was showing correctly in the wardrobe.
??? Pants and any item in the waist zone has a cut out for the thumb. I would like to have an item to cover that up so I can use upper body mod items as shown in the OP without my skin showing through my pants. It certainly does appear that way outside of the wardrobe and I've yet to find a way to cover it. So I would suggest a black filler to put under my shorts in my current avatar, for instance.
Ah, I'm sorry, I misread. I thought you were seeing the weird issue it's had recently in the new wardrobe. I misunderstood. I'm not sure they'll ever stop doing cutouts entirely as plenty of people do like their hands to appear outside the clothes when not removing limbs, but it would be nice if they'd maybe make a simple transform option to new items so you can set it to either be full or have the cutout. Or do like you suggest and create a set of basic colored thumb covers so you can make it appear as if there's no cutout.
Although I don't think I'd use this feature (the limb removing one), I support the creation of an item like this. Having the little thumb gap is distracting!
i have been running into this lil problem more often these days, so something to mask the thumb gap would be really nice!
Still want, these would be really "handy" in wide variety of colors (like the basic shoes). ;)

Thanks, I hate it.

110% support! loved the newest shirts until i saw mention the problem it causes and it's SO OBNOXIOUS ASDFKL
there's far past negative chance they'll ever revamp thousands on thousands of wearables (we still have items with the old avatar silhouette cutouts years after it was changed, there's no way in hell they'd bother, and CWs wouldn't be able to change even if they did)
[egg=roadkill] | | [tp=roadkill]
I support this, and I don't even wear clothes!
I'd be happy for a belt in a relevant color.
[edit]I just tried one of the newer, longer sashes that sit low on the waist and all that does is make it worse. Item in question is this:

It would be incredibly helpful

For close fitting items like shorts, maybe in addition to the thumb fillers there should be some basic underwear in zillions of colors like the tights we aleady have. Black tights might fit under those pirate trousers.
Definite support! In the mean time here's a list of items I've found that cover up the thumb! Will edit if I find more! [spoiler=] + recolors +recolors +recolors +recolors +recolors +recolors +recolors [/spoiler]