Shon
On the BAe146 with the operator I work for, we have guidance in the type SOPs (Standard Operating Procedures).
Basically if the aircrafts actual BRW (Brakes Release Weight) is within 600 kg of the RTOW (Regulated Take Off Weight) we come to a halt, advance the thrust levers and don't release the brakes until achieving 60% N1.
If the BRW is within 400 kg of RTOW we must set takeoff N1 prior to releasing the brake as well as ensuring that we do not compromise the line up allowance used to calculate the RTOW.
Why?
Basically to ensure that the RTOW is not compromised so that in the event of an engine failure there is adequate performance for obstacle clearance.
If say we did a rolling start at BRW = RTOW, it would be quite possible to have take off thrust set later than the performance calculations assume. Thus aircraft acceleration would be slower than predicted and the aircraft would be further down the runway when it reached V1. A rejected take off could see the aircraft over run the runway end.
If by spelling out the abbreviations I'm telling you how to suck eggs, please accept my apology