WGU,
The speedbrake issue has nothing to do with Green Dot. If you leave the speedbrake out in many configurations it is possible to force the aircraft into Vls without turning at all. You have just removed lift from the wing so the min speed has increased. I think that argument is a red herring, we often have to modulate the amount of speedbrake selected to keep above Vls.
Icare, being trite the logical conclusion is that we must descend on the arrow. If the FMS says decelerate, we must decelerate. If we are above the FMS calculated vertical profile we must use speedbrake to achieve it even though we know it is incorrectly calculated.
It does not say in the manuals that we should put out the wheels before the flaps but sometimes going to Moscow you have to do it. Flying below Green Dot is an alternative just like selecting Flap 2, Gear down and flying at 180kts to get down to platform rather than decelerating and descending, which never seems to work as well. Surely (Don't call me Shirley) as pilots, it is our job to apply airmanship to come up with an appropriate solution in any given circumstances from a range of options.
The actual definition of Green Dot may surprise you, it is the 'Engine Out Operating Speed in the Clean Configuration' which also corresponds to the best lift to drag. It would therefore seem to be pretty stupid to fly below it with full power on but in a descent at idle it may well not be the worst thing to do. Interestingly though during clean up on take off we do fly below it with full bore on the jet every day. Worth thinking about?