Altering the Nobirus

Lets say for my theoretical campaign I wanted to alter the Nobirus so that instead of the build points invested in the race stacking with divine build points, they would stack with fighting build points, so that it’s possible to create a progeny of a god that exceeds at war, like how Achilles is portrayed in the movie Troy.
How would this change the XP adjustment to the Nobirus levels. Would it be:
0 = 125 XP
1 = 625 XP
2 = 1,125 XP
3 = 1,625 XP
4 = 2,125 XP
Or perhaps more? There is no other race that stacks fighting, so the values may be skewed. Also, would this prove to be unbalanced? Uninteresting?

Talath, it looks like you have the math more-or-less correct. If you go that route, please let me know how it turns out.

I shied away from letting any race fully stack with Fighting for fear that it would be too powerful. You might take a look at how I handled the Thrassians, which half-stack with Fighting.