Intruder,
Now I agree somehow.
I am an Airbus driver and similiar to Boeing the small index below the sky pointer on EADI shows lateral acceleration, which is equal to skid ball on conventional planes.
Why I am sure somehow Side slip is measured or estimated in Airbus, because that slip skid indicator on Airbus changes to show side slip indicator in Blue Color (They call Beta Target) to show the amount and direction of side slip in the case of Engine Failure at take off. And the pilot is advised to use that side slip indicator to minimize the side slip which also minimizes the overall drag of the plane at that critical situation.
My curiosity, there is no weathervane -as you also mentioned- on the plane to measure the sideslip. On photos of A 380 showing the nose section, I noticed some weathervanes just in front of windshield which is aligned with longitudinal axis, whic I guess is used to measure Sideslip. But not on the other Airbuses. So I guess there is another method to measure sideslip, for example on A 330, which may not be so accurate as A 380 though.
That is I am wondering about.