Deleting root bones without skeleton moving/rotating?

[ficool2]

So I am fixing up some of my old TF2 weapon mods from 2009. These are rigged onto the Valve biped and have custom animations. The problem is they are a v_model so I have to convert them to use c_models. Anyway, I am running into a problem with the armature. The armature is organised like this:

0 "Bip01" -1
1 "Bip01 Pelvis" 0
2 "Bip01 Spine" 1
3 "Bip01 Neck" 2
4 "Bip01 L Clavicle" 3
5 "Bip01 R Clavicle" 3...

I need to remove the bones Bip01, Bip01 Pelvis and Bip01 Spine. However, upon removal, the skeleton loses its rotation and position and becomes a mess. So my question is, how do I remove these bones without the skeleton moving or rotating? (Basically making it stay in its place after removing the root bone)

[xdshot]

You'll probably need to duplicate your old mesh and re-rig it on newer c_ skeleton. And re-animate it. The easiest way is to use constraints.

[Dota-Art]

You need to pass parent bones's animations to a childs's bones and then remove the needs's bones.