Not necessarily. Even if one takes that statement at face value for a literal truth a balance problem can always be solved by tweaking, and for a developer with a long track record at building First Person Shooters it shouldn't be that difficult not only to work those problems out but to build a decent rule set to inform what else is added onto the sandbox (supplementing common sense.) The tricky part is just balancing the major weapon types against each other but once that's done the variations of Assault Rifle, Sniper, Shogtun, ect. can be pretty easily added to the game (see. why its not a problem for games like Counterstrike or Rainbow Six to throw in a dozen variants of the same weapon class.) Its more or less just a matter of initiative. Bungie could be building up a large, amazing sandbox but they're opting instead for a "type 2" structure of weapon design (that's one to all my Magic the Gathering homies out there.) Maybe they've got similar reasons for fearing big-ness, but in a game that was originally sold on the feeling of being 12 years old again and playing in an epicly fun world that fear seems to be entirely misplaced.