The devs actually said they are working on new sleeping poses for all races!
(sorry, don't have the link to the post at hand, but it's somewhere in this forum)

The main assumption why we are not allowed to have a /playdead emote or just generally lying down on the ground, a bench or whatever is beneath us, is that it will be abused to make it seem as if characters are doing naughty things,
and that even people who do not want to participate in that kind of thing will be molested.
And I'll say it again...the amount of times that lalas humped my legs and catgirls groped my chest are so numerous that I gave up counting. If people want to do that kind of stuff, they will do it even if the only emote you give them is to smile.

For /gsit, I imagine that being a bit harder to implement since it would actively have to ignore the furniture? If it's not too much hassle, it would be nice though :3