Yes, it seems a bit mind boggling as you are now roll playing each of the characters and decide the decisions for yourself with the other party members, if you decide to take them. It will be strange but fun at the same time as you have an idea and feeling for each of the characters, like this team should do the non-legit way and the other do the legal way BUT there is parts where it can clash. Where you may have to fight with each other BUT do I control everyone in the fight and decide which people in my party to win and how it will affect to the end game as you describe.
For example how about if there is a mission where you have to assassinate someone and the other party have to protect this NPC or get the NPC to a secure destination for them to complete the quest. On the other end the other party may ambush, assassinate the NPC in his first location (if other party did not make it) or have to battle it out on a secure location (if not make it to their first destination where they have to find clues or paths)
I wonder if you can bribe each other with RPG elements like if you let me kill him I will give this and this or share your rewards and that quest giver for thw assassination will not like to pay double or have not agree to do this arrangement and decide to kill both party's. Or that NPC that is going to be assassinated will pay double from the original quest giver and may decide to not pay the ones that was escorting the NPC. Where it might go like this, the assassins party take the money from the NPC and now the other party who was escorting the NPC will kill the NPC and decide to take the reward from the assassination quest OR the other party will take the money and still kill him and get even more rewards lol.
There is allot you can think about when designing this quest lol but I am unsure how well it will be when playing alone as you have to set the schedule and you are deciding which party wins.
It's pretty much something awesome but I know that there are many people who would love to still play SOLO without doing this to themselves lol.