When a UFO shoots down an XCOM craft over land, it should generate an XCOM crash site.
The player can launch a transport craft with soldiers to rescue any survivors at the crash site. When they land, the battlescape should show the crashed XCOM craft and the soldiers in it who should be wounded and/or stunned. The rescue party will have to use medikits to stop them bleeding out or carry unconscious casualties onto the rescue craft and then take off.
If the player delays and does not launch the rescue mission soon enough, the aliens launch their own crash recovery mission:
The aliens start a mission to salvage the XCOM craft and abduct survivors for research. It could involve abductor or harvester that goes and lands at the XCOM crash site.
When it lands, the XCOM crash site becomes an alien salvage site. The player can launch a ground assault on this site which will be like the rescue mission except that it now also contains a landed UFO with hostile aliens.
A successful rescue mission will recover surviving soldiers and equipment from the crash site, as well as some scrap metal and craft parts that can sold.
