I'm not familiar with flight path vector indication, but must work off the IRS? A quick ques on it's use as you describe....
Suppose on your 777 you have entered the SID required gradient, and come up with a required climb angle, and decide to fly this gradient. Eg 3.3% gradient gives 1.88 degrees climb angle. Will your flight path vector show 1.88 degrees in the AI?
Now you go from zero wind to a 30 knot tailwind. Does the flight path vector increase to a higher climb angle to ensure the 3.3% gradient?