Thank you for sharing your actual problem statement. Now that I understand your problem quite clearly, I think I can contribute better.
As seen from the figure above, I notice that this pin and shaft (PS) system is going to rotate with the help of electric motor, now my question is:
1) If the WP is rotating continuously or just momentarily till you rotate it by a small angle ?
2) Also the shaft in your PS system seems like a flange or a coupling between the Pin and the WP (to transfer rotation from motor to pin to WP) ? Or is the shaft part of the WP which is mounted over the pin with the help of linear actuators ?
For first case, continuous rotation of WP: (a bit complicated but we can solve it with discussion)
I notice that the CG of the workpiece (WP) is not co-axially aligned with the PS system and I hope you have done or will be doing fatigue effect because of the centrifugal force (as you correctly mentioned) on your PS system which is going to be major concern in my opinion (Also assuming its a balanced WP system, if its unbalanced you will have to balance it before doing fatigue analysis or calculations which ever you prefer)
For second case, rotation of WP by small angle: (Easier of the two cases)
If the angles are fixed, do a static loading at 90┬░ rotation (which is worst case scenario in my opinion).
I agree with what you did to simplify the problem, symmetry and halving the load is right, but it can be simplified further.
I feel like yours is a static case and then centrifugal force need not be worried about. You can transfer the Weight force (F=mg) from CG to WP end of the shaft. All you have to do is shift it parallel and add the moment at the WP end of the shaft to make it statically equivalent system.
So basically your focus is to design a holding mechanism for the WP and rotate it by some angle to work on WP maybe. I still think there won't be an axial thrust on the base of the turrets, unless you bring the actuators very close that the WP is applying force on the top end of the turret via the Pin (IDK if this explanation is clear or not) All you actually need to worry about is the moment (which is also a kind of force on turret base if you think about it)
Kindly let me know, if my understanding is in line, if not, please correct me.
Mention which case are we talking about and we can discuss further (I hope this isn't very urgent considering we can contact only once a day, probably because of the time difference.)