If you plot all the SID tracks on a map with unrestricted climb to 5000 you'll see it is very difficult to get an opposite direction light aircraft through that.
ATC's are paid very good money to separate aircraft. There is full radar coverage in all capital cities with most of them having ADSB coverage. There are plenty of options available to the situation described by nosewheel. Seriously, who cares if there's an opposite direction scenario. It may be difficult, is it impossible? Digitus extractus comes to mind.