we have in the past! but it does take a few extra steps, (more work in the long run). for one, sketches can't use layered elements without specified rigging for them (expression overlays and minor transformations require pretty pixel exact measurements to be seamless). developing that sort of stuff for sketch artwork is possible, but most of the work has to be replaced when the assets are re-done.
the other aspect is the backgrounds. imparagon's clipping issues are less noticeable because the backdrops are primarily white, so you don't notice when there are errors in the fill layers. it would be more feasable is fall of royale harem's backdrops were also sketches, but the variety in tones and shades makes mistakes quite obvious.
in all likelyhood, we will do sketches again when we need to cover alot of ground, but will avoid using overlays for these reasons (for example, we might sketch out draconoclast muscle rhianna, but it won't come with BE or Melon minor tfs). the reception wasn't great the last time we did them, but we'll see.