While someone like BB can give more definative answers, I can address a few of these points.

A painting room: Take a look at the size of the code on Gimp or Photoshop. That is what you are asking to be added  into Poser. That's an awful lot of overhead to drag around for functionality that will be used only a tiny percentage of the time. Gimp (The Graphic Image Manipulation Program) is available free and gives you plenty of paint tools to modify your maps.

Reendering in buckets: This is what I THOUGHT we had in the current multi-computer scheme, but I'm told it is not. The current distribution is (I think, subject to correction) only useful in animations, rendering full frames on different machines. I'm with you and am wanting to see distributed rendering, but I have a feeling it is a true bear in terms of programming. I have no idea what sort of code overhead we are talking about here.

The idea on the figures... I have no idea about. I don't model. Perhaps some of the modeling artists have an opinion on this.