I guess if you really need to pick a different fix, then I understand if that becomes an issue. I myself never really need to pick a different fix.
In your specific example, if I need to fly to KSNA and the active runway is 02L. I just pick the OHSEA2 02L on the Arrival pattern and the RNAV 02L-Y from the approach list. And that’s it. That’s all I need and I just pick FLY.
And the dev version of FBW aircraft will take all the STAR and the Approaches with the ATC will follow suit as well and the autopilot follow them.
To me when I look at the flight path and as long as it doesn’t look weird like the above screenshot, I really don’t see the need to pick a different fix.
If the active runway is 20R and I want to stick with the same STAR of OHSEA2, then I just pick RNAV 20R-Y and pick the OHSEA2 20R Arrival Pattern, and it becomes this.
Or I can choose a different STAR that also positions to runway 20R as well.