I don't really know much about complex art programs and implementing such things in games.
I am designing a game and I want players to be able to do certain things:

I want to enable players to paint murals on the walls of player made buildings
I want players to be able to do things like change their hairstyle and make tattoos
I want to allow players to craft gear and modify it to a significant degree:
I will do some examples here as its less clear what that means:
If a player makes a staff from some wood, I want them to be able to do things like carve the shape of the staff.
If a player creates a robe of frost dragon skin I want them to be able to take sheets of the material they got from
skinning the dragon and be able to do some simple tailoring.
If a player wants to add some decorations they should be able to add things from their crafting supplies. Say they
have the frost dragon robe and want to line the hood with phoenix feathers. This won't affect the item stats but
it will change the appearance of the item.
I want players to be able to construct buildings and other large physical objects like statues from various materials:
Again some examples:
Say that a group of players are roleplaying as dragon slayers, and actually work to slay as many dragons as they
can. I want them to be able to build a city out of dragon bones and skin. One particular method would be using
ribs as the structure of a building and covering it with dragon skin.
I would like them to be able to do things like construct a frost dragon head shaped town hall in the center of the town.
More examples
They could do something like use marble to shape the building in small squares/triangles/other shaps and then carve
sand or grind the sharp edges down to make the curves. Then they could paint it. Or they could use blue veined marble.

I know this sounds like a lot of stuff but I was thinking I could give players a built in art tool and they could transfer to a crafting UI screen and select materials and put them together here and do like, digitally modeled carving or something. And if they had access to dyes or paints ingame they could access those items here and use them to do colors.
Presumably it could be done using the same art tool as I used to design the game in the first place. After they finished carving or even if they were only part way done and had to go they could click save and it would switch the altered model into the game in place of the unaltered item. I suspect it would be impossible to carve in real time, so you would probably only see the original item and then like snap shots of the process as they saved the item and then came back later.

As I said I am not up there on my art tool knowledge so maybe this is crazy.

As I said I am not up there on my art tool knowledge so maybe this is crazy.

Yes, it is.

You are talking about a very powerful tool, which is a difficult project on its own. Take a look at tools like poser.

[quote name='AltarofScience' timestamp='1328201367' post='4908763']
As I said I am not up there on my art tool knowledge so maybe this is crazy.

Yes, it is.

You are talking about a very powerful tool, which is a difficult project on its own. Take a look at tools like poser.
[/quote]

Which parts are really difficult and which parts are possible to do?

Which parts are really difficult

Pretty much all of it.

and which parts are possible to do?[/quote]
Possible? All of it. Feasible in a given time/on a given development budget? Probably only a small portion of those.

You are I presume familiar with Spore, Little Big Planet, Minecraft and Dwarf Fortress? These games are pretty much the state-of-the-art in user generate content, and all of them place very tight restrictions on what elements of the world the user can modify.

[quote name='AltarofScience' timestamp='1328278460' post='4909163']
Which parts are really difficult

Pretty much all of it.

and which parts are possible to do?[/quote]
Possible? All of it. Feasible in a given time/on a given development budget? Probably only a small portion of those.

You are I presume familiar with Spore, Little Big Planet, Minecraft and Dwarf Fortress? These games are pretty much the state-of-the-art in user generate content, and all of them place very tight restrictions on what elements of the world the user can modify.
[/quote]

Yes I know them all.
Which parts of the list will take the longest time to deal with? I presume altering static items like weapons and buildings would be easier than dealing with moving things like haircuts and clothes.