Any one worth their salt will address the twitching rear blendspace by isolating it into its own blend space 2d.
however, the content examples did not use blend for movement, they implemented the speed warping node which scaled down the animation via ik bone manipulation.
Similar with the actual rotation, they had a node that specifically turned the character spine and matched the pelvis.
I think you should branch the system and offer both ways if you still have the code… the blendspace way is very common and a great thing to have. The anim sequence is used occasionally - mostly by those who won’t rely on the blendspace not even for speed.