Is there a way to avoid vehicle lane changing immediately in front of stop lines (signals/priority rules)?
Yes. For a short section (e.g. 20m) in front of the stop lines, apply the 'No lane change...' flag in the link/connector attributes to all lanes and all vehicle classes (you may need to split a link in order to get a suitable section).
Caution: A gridlock situation may appear in that section as no lane changes are possible - not even necessary lane changes because of a route.