Support for ESRI i3s (.slpk files) was released in FME 2018. This includes 3D features such as buildings, but currently does not support writing point clouds. Adding support for point clouds would allow these to be uploaded and viewed within ArcGIS Online web scenes.
I3S writer:
https://docs.safe.com/fme/html/FME_Desktop_Documentation/FME_ReadersWriters/i3s/i3s.htm