In the pop-up window before confirming the rebuilding, as shown on the screenshot above, it is said that "All animation and poses will be lost" even though the option "Preserve Keyframes and Channel Values" is enabled.
Also the option "Add "Rapid Mesh" to Rig ( if Mesh does not already exist )" makes me think what will happen to my already skinned mesh which does exist. Or is it about the Rapid Mesh? And even if Rapid Mesh does exist (in further rebuilds), will it be updated, keeping its edits, or overwritten with the new one?
The "All animation and poses will be lost." will only appear in the dialog window if "Preserve Keyframes and Channel Values" checkbox is not checked. I added "Rapid Mesh" to be more specific in the parenthesis of the Add "Rapid Mesh" checkbox.
Currently, rebuilding a Rapid Mesh only remembers the width/height/depth values of each geo's attributes. I need to do some more testing for storing the vertex positions of all the geometry because this will definitely impact rig rebuilds to store and move all those vertices. I haven't had a chance to see just how bad it is before I decide how to proceed with that.