I am not sure if I get the whole idea but I think this is going to be some kind of action RPG, meaning that there are not much arcs (starred by Peanut) that could be useful for it.
The only ideas I have by the moment are these:
-We're snowed in: Peanut goes to visit Tarot in the middle of a snowstorm and when he arrives to Sabrina's house he learns that the neighborhood is being attacked by the frost giant Aurgelmir and Tarot is fighting with him right now in the spirit world. Then he and Sabrina decide to go there and help her (you know, with some borrowed powers in magical items as we saw in Temple Crashers).
Basically, the game consist in pass through the diferent spirit realms, fight with magical critters, defeat the bosses (Minotaur, Grognak, etc) and the final boss Aurgelmir. Also, there's the chance to do some side quests helping some inhabitants of those realms and purchase special items in their shops (as we saw he did in that sort-of-gas-station).
Regarding skills, I'd say Peanut should specialize in a short-range weapon (because I think it fits better with him and besides the game would be boring if the only possible attacks are long-range). However, I do not recomend a heavy weapon but something lightweight and maneuverable such as a Gladius (short sword) or a lance. Hand to hand and magic doesn't fit with Peanut at all.
Sabrina is more of a support character and a guide who tells you what you should do when you have no more ideas. Her abilities should be the same as shown in Temple Crashers (short-range teleport and elemental magic). Of course, support characters tends to be weak so having someone to protect will give some difficulty to the game. Also, she could be the key to solve some side quests.
-The great Water balloon war: I recomend a spin-off of this arc, following Peanut's actions this time. A sudden war between cats and dogs is unleashed in Babylon Gardens and he is the only one that suspect there's something evil behind the scenes. He calls a truce with Grape and convince her to act as a double agent for the dogs with the purpose to gather info from both sides while he does his own research. While he do this he'll be suspected of treason and will be forced to confront both cats and dogs.
The game consist in fight with random cats and dogs, defeat their bosses (Max, Marvin, Fido, Rex, etc) and collect info from the spies (Grape, Joey, Tiger, Zach) and from the defeated bosses. After Peanut is kidnapped, he'll have to find his way out, fight with the final boss (Keene) and escape before the building collapses.
The armament should consist in water balloons and pistols for everyone, though of course the kind and power may vary depending of the character.
That's all I can think of for now. I hope you find it helpful.
). I'll be sure to try and make that happen! 
. My hopes are that they notice that this is happening by me releasing the concept and putting it in the comic's DA group, though for some comics I'm okay with just asking them. And I'm pretty sure Rick already knows about this project, seeing that the peanut concept is in the DA group, the forum gallery, AND has it's own topic in said forums. 
