I would contact long arm quilters before you purchase the blanket to see if any of them will tackle it.
I made one quilt using a 100% wool blanket, but not an army blanket. The blanket I used was much softer than the WWII surplus wool blankets that I grew up with, but the newer ones may be different. Make sure that it is laundered so it doesn't shrink, or run. The quilt itself came out much stiffer than if I had used batting, but it was OK.
I guess I'm curious as to why you want to use a blanket vs. a batt, or does the one your mom currently uses have a blanket instead of a batt.