>>19201794
>I figure that even if you only have at most 500 men in powerarmor, its worth at least 50 000 average pdf.
Nope. You need bodies to actually occupy territory and hold battle-lines. The good fluff for Spess Mahreens acknowledges that they're more of a pinpoint response, able to take out specific targets or fight local battles, but unable to maintain any sort of large-scale battle, much less an occupation.
A company of 500 men, no matter how well armed, would only get isolated, surrounded, and piss-pounded by a force of 50,000. At best, they would have to be evacuated by some sort of airlift, but that's not the same as winning.