When playing with the option for a limited alien containment (10 aliens), sometimes it happens that the containment is full and all further aliens captured are automatically killed.
In case of a full alien containment, it would be really nice, if one can choose which alien gets killed.
In my opinion, UFO apocalypse featured the best alien containment, where you had an own screen, with a nice overview on all aliens (also corpses) and the remaining containment space. This information is also available in openXcom, but scattered over several screens.