Hm... Possibly spoilery question, but I still feel the need to ask, so I'll keep this short..Will it be possible to help out a rival gang?
What do you mean to help out? I don't want to spoil it but there will be an option for many even most unlikely endings related to the gang :D
Like... Doing favors for a rival gang that undermines the Hyenas. Anything from simple parcels to, well, you can guess.
