Sorry, but sounds like a terrible idea as Sans. do not like humidity, seems an invitation to rot. Succulents in general don't like humidity & needs lots of air circulation to thrive, & Sans. are succulents.

If it's left uncovered, it won't be high humidity. Plenty of terraria have succulents, or even cacti.

But succulents tend not to do well in them, we see folks coming w/ problems in these pretty often at the Cactus & Succulents Forum, don't know if you go there Hoof Maiden. The lack of drainage is a problem too, irrespective of what kind of mix layers are in the Terrarium. Lack of air circulation in there is a problem too, no terrarium cover means just that, it's no indicator of any air movement at all.

There are so many other, more appropriate plants to choose from for Terrarium that wouldn't be a struggle, I'd consider those instead.

Hoof, lmontestella is quite correct. Succs and cacti make very poor terr plants. They are sold that way because it looks "cute" and people buy them.

A Sans might be doable as a temporary/short term display setup, but I do not think it would be workable long term.