Power Armor could be introduced the way Bozar and Gauss Pistol are. That'd be very nice, as it'd make it very rare, yet accessible and visible from time to time. I mean it's not like PA was restricted to BoS in the year 2238, for example you could buy the suit in San Fransisco, you had mercenaries/bounty hunters wearing it and compared to the Enclave tech T-51b was pretty much outdated. The Armor itself is not really overpowered, and with 2 or 3 per side it wouldn't really change the way battles flow. It'd basically be the same as CA/BA 2 wipes ago - very rare, very much valued, yet appearing from time to time instead of being stuff of legends.