Well animations are work in progress. Although they won't change too much. Basicially up and downstab need to be fixed, because at the moment they do not go very far, which makes it hard to hit people that are further away. 1st picture obviously shows a upswing that you would normally only do when the bayonet is not attached.
Functionality for that is there. Basicially you can attach and remove the bayonet. Not having it attached will give you 4 swings, the upper swing of that is shown on the first image. When the bayonet is attached, you only have up and down stab.
Right now, the bayonet mesh is not being removed when the bayonet is not attached, that is why you can see it on the first image