I just re-read your post and may have given the wrong information for your situation. The question is do you want the S/E markers to just refer to one set (the A5 set) only, or do you want them to refer to both sets?
If you just want them all to refer to one set only, just use the refer to Drawing to link to the drawing in the A5 subset. Furthermore if the views are the same for both sets, then you only need one view, instead of creating two separate views. Then you can use Refer to Drawing to link to the view. In this case it will automatically link to the drawing that was placed in the subset first. So if you want to link it to the A5 set, create (or now recreate) those views first, then create your A4 set.
It can be a bit confusing, especially since the link doesn't appear to stick to the view, but it will!
Hope that helps.
Cheers,
Link.