Ruserious,
At Hong Kong at CLK in single runway days,we used a cut off of 3 miles for the inbound and positively rolling for the outbound.This worked well with the large number of heavies,to get the ICAO runway length.(3900m)The inbound got landing clearance at about 1mile ish.
At HK we had to increase the gap slightly,because of the Cargo a/c sometimes using the whole runway.Also a/c stopping on high speed exits was a real problem.
In the UK,you can get later landing clearances,as the outbound just has to be airborne and not passed the upwind end of the runway.Also some places can land after the departing with certain criteria.Also we can't use immediate departures with heavies.They obviously can't move fast and there are concerns about a/c at the hold behind.
As far as vortex goes I will note the minute and second that an a/c rolls to get the 120sec,or 180 secs behind.Also waiting until the previous departed has passed 4 miles outbound will give 120secs vortex.
I would never tell an aircraft to vacate at a specific exit.It's just asking for burst tyres,or hot brakes.We often used vacate at the end,and it was just as quick as they didn't come to a screaming halt.A lot less grief for the engines and brakes but the pilot has to play the game and not think he has squatters rights.
Anyway I don't work at Dubai(Deemed not worthy by Serco),but that's what we did,with the ICAO rules we had.
