I have been playing in monster play for about a month now and I have came up with a few decent ideas for new monster classes.
1. A playable (purchase required) drake class. As a drake there would be the option to change to frost or fire drake.
2. A new Moor extension to the left of "Steps of Gram". This extension would host a new outpost that looks like something from First Age Gondor. (Delving would be extended as well and would contain a new boss similar to the Nazgul)
3. A playable class similar to the Black Riders (What Amdir turned to in the prologue). This class would be purchasable as well.
4. Allow GV raids. Creeps would now be able to enter GV and take captives. Freeps would also be able to enter Gramsfoot. With Creeps capturing freep NPCs at GV, a capture the flag (NPC) mode could be established. There would be specific infamy/comm boosts for every npc captured. The goal would be for the Freeps to enter Grams and save the captured npcs, escorting them back to GV. To prevent farming there would be a time limit in between captures AKA a cooldown. (Creeps cant enter GV until 30 minutes after their last capture).
I think this would be a great addition to both Creep and Freep Play.