I loved the single texture for Posette, even the transparency was on the single map and with renders under 2048x2048 a single map of say 4000x4000 provides an excess of data.

A variation somehow of the standard V3 layout but placed on one texture plane would be great since the V3 uvs are nice and if it was done right a very simple Photoshop action could convert any existing V3 textures to the new layout.  Basically the V3 head map items could be stacked as-is over the body to make a simple layout. Just have to fit the eyes and teeth/gums somewhere like above the neck between the arms and leave the existing transmaps I guess.

Probably the most useful figure now would be a V4 17K LOD mapped to a single texture like that. There is really no reason to use V4 instead of the V4 17K LOD converted to Poser. 17K is plenty mesh resolution and the figure would use the new clothes out now while most people have plenty unimesh textures that could be easily converted. There was even a tutorial here I used successfully to make a lo-res M4 from the V4 17K mesh. It would be simple to shape the V4 LOD to V3 body shape with the V4 to V3 mesh and from there even to V2 or Posette if you want since there exist V3 mesh in those shapes.

Anyhow... just me dreaming.