Gonzo, I think you have the wrong idea of 'departing'. When an aircraft
departs from an intersection, it means he has
lined up there, and starts the Take-Off roll from that intersection. The Rotate and Take-Off point will be towards the far end of the runway...
Pilots of lighter aircraft often ask for departure from the most convenient intersection, if their aircraft does not need the full length of runway.
Multiple Line-ups on the Same Runway - SKYbrary Aviation Safety
Given similar types of aircraft, the second aircraft will always be flying under the previous aircraft's wake Turbulance. So you should never cross that turbulence, unless you deliberately try to out-climb the leading aircraft.