Rather than just a regular hero, how about a 7th player who sits in virtual reality as the Patron for your team looking down on the city
Their gameplay would be something like Abathur from Heroes of the storm, working at a macro level to supportt the team objectives.
Skills:
1. Candlemaker - Deploy an additional trooper to a lane, or redirect a trooper from one lane to another.
2. Boon - bestow a temporary buff on a team mate, these may be upgraded similar to the itemshop
3. Avatar - take control of a walker or the base patron use their attacks directly, like swatting at flies
4...
