If you really want to use it.. i'd say Two Strike Squads, Six Man Termie squads, run the Libby as your HQ and add the Grandmaster later if you're at higher points level. Run both strike Squads in Razorbacks with your choice of weapon just to get more firepower on the table and take that Dreadknight and Two-Four Dreadnoughts..
Really you could use the PAGKs in Purifiers if you wanted to and that would justify the Halberds to some extent and give you a decent reason to run the Razorbacks. Incinerators would work especially well with Purifiers, but Strike Squads on the Deep Strike could make just as much use of them. If you're taking the Purifier route make sure you use our special GK Detachment so you only need 1 Troops selection mandatory, since you can cover that with the Terminators.