this has been the way of the "victoria" figure starting with the v3 you love so much.  she couldn't take any of my hundreds of v2 textures, morphs,etc. 

what would you have be compatible?  if it's morphs, you can't change the mesh.  if it's clothes and morphs, you can't change the mesh, grouping or joint parameters.  if it's textures, you can't change the uv's.  if it's all of that, well, the most you can do is add morphs.  and we have lots of v3 morphs, and they're not considered a new version.

think about what a new "victoria" means.  a new figure, almost by definition, means new mesh.  which means new grouping and joint parameters.  you might was well map it better than you did last time.  and you're going to need new morphs because it's a new mesh.

basically, there isn't a way to make a substantially new version of a figure and have it be compatible.  it's the same thing when people talk about "fixing" miki rather than replacing her.  they want the forearm issue fixed, but everything else compatible.  but the technology simply doesn't work that way.  to improve a joint, you really need at least new jps and new groups.  that means your morphs are shot.  so you need new morphs.  you could use the same mesh, but you've already  broken morph and clothing compatibility.  it makes more sense to optimize the mesh to improve the jps you're working on.  so now you have a new mesh, new groups and new jps.  well, you could go through the trouble of mapping the new mesh exactly the same as the old one as if you haven't learned anything about mistakes made with the first one.  or, as i would like, you could just provide the old mapping as an option.  but since you've broken all other compatibilities just to fix the issue people were complaning about, there's no real benefit to letting yourself be hobbled by the old uv mapping.

i'm sorry you're disappointed.  it sucks to spend money and anticipate something for ages and then get let down.  i personally really wish someone would remap v4 to take v3 textures.  but what did you expect to be compattible?  to address the bending problems everyone wanted fixed meant nothing but texture maps could be compatible.   please don't get me wrong, i know she's missing a lot of things she should have.  people are raving about the initial price, but i'm also hearing that ethnicity and muscularity will come out in separate morph packs.  so we don't know her full cost yet, and i've witnessed again and again that it's easier to pull $100 from the community for 5 small sets than $40 for a single complete one. i'm hearing different different problems from different people.   but v3 "compatibility" is just not possible without leaving everything about victoria the same. 

oh, and the new figure is actually much, much closer to a standard or generalized female in proportion than v3.  much more neutral.