How do I change the skeleton path that the mesh connects to? Like link a piece of armor to a skeleton so it animates correctly? And can it be done in nifskope? That would be prefered, as modeled edited in blender by me crash the Constuction set.

this is called skinning/rigging.

you can bind a mesh to a single bone in nifskope, by using a NiStringExtraData node named Prn. And in the string field set it to the bone you want in to be attached to. This is how all weapons and shields are attached to the actor and many helmets too.

But for anything that will need to be attached to multiple bones and have blend weights, you need to rig it in blender and export it from there. This is not something that can be done in nifskope.

And about that, is there any reason why blender rigged models crash the construction set?

There are loads of reasons rigging models in blender could cause it to crash, just as there are with modifying any model through any tool. You are probably doing something wrong (I think the .nif exporter supports exporting rigged meshes now), but I couldn't tell you what it is unless I saw the file you were exporting from. I believe there are some bones that you shouldn't rig to or include, so that may be an issue, or perhaps you rigged a single vertex to multiple bones over 1.0 effect, which might cause some funny stuff.

Like the people above mentioned, you can't do what you want to do, in Nifksope. You have to use Blender.

Firstly, make sure you have Blender and your other programs installed, as mentioned in this tutorial, just in case:

http://www.tesnexus.com/downloads/file.php?id=12248

From above, you should choose the following program versions -
Blender 2.49b
Python 2.6.5
Blender NIF Scripts 2.5.5
NifSkope 1.0.22
PyFFI 1.1.5

Secondly, this is a handy site with some Blender info that might come in handy for you later on:
http://niftools.sourceforge.net/wiki/Blender

Skinning, as explained by this site (does not tell you how to skin, but tells you how it works):
http://blender.active-domains.com/x/x5248.html

Blender.org's Skinning Feature(s) (note the "Bone Heat Weighting" option):
http://www.blender.org/development/release-logs/blender-246/skinning/

I have made a picture tutorial for you, in regards to skinning in Blender (download the images, and look at them in order starting with "1a" prefix and ending with "10"...):
http://img153.imageshack.us/g/1aaddarmaturebonestosce.jpg/

Lastly, here is a quickie tutorial that goes over Blender Rigging, and then Skinning (on the next page):
http://blender.active-domains.com/x/x1370.html

To make custom armor bend with vanilla NPC's bodies properly, try to do the following first:

Import the NPC skeleton.nif from "_male" folder, and also import all the body meshes of either the male or female into same scene (chest/arms, feet, legs, etc). Make sure the meshes are parented to the skeleton.nif (Blender has an option upon Import to do this automatically).

Take your armor piece, and make sure it is separated into the different body parts that Oblivion uses: Boots for feet, greaves for legs and waist area, etc. Add an "Armature Modifier" to each custom armor piece of yours (look at my picture tutorial: 1b through 1d)

Then first select your boots, and then secondly select the vanilla body's feet mesh so that both are highlighted (order of selection matters), then go to "Objects' -> "Scripts" -> "Bone Weight Copy", make sure the quality is set to 4, then click ok. This will make it so that your boot mesh conforms to the weights of the vanilla body mesh's vertices, and bends like the vanilla body part (for the most part).

If the boots show some vertices acting weird, you need to individually tweak those vertices weights in the "Weight Paint" section (shown in picture "10" of my picture tutorial).

Do NOT skin any vertices of any Oblivion creature or NPC mesh to the Bip01 bone. Do not assign more than 4 bones for any individual vertice to be weighed to. Creature meshes, NPC meshes, and armor/clothing meshes - when exported, they should NOT have a Bip01 or Bip01 NonAccum bone in the listed bones, in Nifskope. Having these two bones in such nifs, also causes CS error message, I think.

Koniption