Mostly, the features are related to User Interface and backend communication. I'd consider using native plugins for both facebook and google logins, and for the website, we'd just use its API to do the job. Anything that has additions, as the slots for map and heroes, could be upgraded into a scalable system that makes it easy to anyone to add new content in, without any need to code or modify the UI directly. Everything related to monetization needs to be very well described so we can have the best interaction there. If needed to change original game code, there might be a little extra time of work, depending on the project organization and clarity.