If you do not have your parallax adjusted correctly you can get a POI shift... As for setting up the ocular lens, this is a set and forget item.
Adjust the ocular one time and then leave it alone... Unless your eye sight changes.
I would call SWFA but only after testing some more things...
I can not say what we will be making in the future, all I can see is JUST WAIT :)
As for the Diopter adjustment, All USO scopes have it - The ER25 is -3.5 to +2.5