Howdy I always thought it would be cool to fight indoors on like a set, having the advantage of cover to make it a bit more interesting. This could be like a kitchen and dining room or maybe a parking lot where there are random cars. Since you bring the topic of the gangster theme, you could work in the elements of the bootleggers where they would meet in random spots and drop their items off to be sold. A lot can be done, movie sets random small little details that make it look alive but is actually a spar. Real world examples of this would be Paint Ball they often times use cover to their advantage. I hope this comment stands out from the rest, and you take my suggestion into consideration. Cheers.