The Maxis “Cloud” chair is the perfect fit for the Antique Writer’s Desk, I think, but regrettably it wasn’t permitted to be a desk chair. Until now!
It also works surprisingly well as a dining chair, and the animations are almost not weird at all (I never paid much attention to how exactly sims slide their chairs back when they leave a table, and I didn’t compare to other chairs now either — they do sometimes massage the air around the chair a little bit, but I’ve seen no broken wrists or anything like that. Also, the foot dropshadow does not slide when the chair slides; I have no idea whether it does that with other chairs).
This is done by referencing the relevant DATA file (0x3DDFE3EE4CF7C09E as in the Mission dining chair) in the SlotTypeSet (UnkIID01) field in all of the COBJs. I also swapped back the swapped swatches of the second and third variant while I was at it (i.e. the blue swatch is now actually the blue chair and vice versa) and edited the catalogue flags to make it show up in both dining and living chairs.
Note to builders: when you use this to place chairs, downloaders need this mod so the chairs be removed and put back (snap into a table) properly.