I would personally prefer ladders in a tiny home. I didn't really stop to consider the full implications that wall height would have on those, though, so that's a good point to bring up. They were able to figure it out with columns recently, so I'm confident that they could make it work. Even if they just gave us 3 separate assets of ladders for each wall height. No need to have the ladder slide like the columns do now, if they don't want to do it that way. You're definitely right that the wall heights do make it more complicated, though, so I can see why it wouldn't be included in an SP. I still want it, though! lol
I have no idea what the hold up is on spiral staircases, but they're not as big of a deal for me as ladders are. I'm not sure they will ever come, especially now that they did the stair update which allows you to rotate your stairwells. In regard to customization and functionality, that update is a vast upgrade over stairs in previous iterations, but it doesn't save you any space and they don't curve... so my space saving loving heart still wants something like spiral staircases. I just like having space saving options, but I have learned how to wrap stairs around the exterior of homes and implement other creative solutions in the meanwhile.