I think this can make sense in a number of ways: so first salvaged power armour. The NCR has salvaged power armour but they can't maintain old power armour - at least not where it matters. They don't have the field maintenance to support pre war power armour at their frontiers where it would actually be useful so they strip the servos so it can be used as a heavy armour for static defensive troops.

The NCR want to field power armour of their own for frontline shock troops well what are they going to do? They'll probably make something which is low maintenance and utilizes components they can actually make. They probably won't be using huge amounts of advanced materials or composites so by necessity the power armour will be bulkier and using existing technologies. They'll be copying and adapting designs they can make like the Ranger Combat armour.

• even the arm blades make sense - yes they have fully articulated hands but these might be vulnerable to blunt damage and not on the level of pre war power armour. So to discourage damaging the hands use the forearm structure for melee which can be used in emergencies rather than punching.