I've actually thought they should limit the number of ships you can take by chasiss not just base size to be able to better cost ships effectively while not permitting spam lists. Y-Wings are a good example I think, we've all seen the Y-Wing spam can be problematic, right now the only way to fix that is increase the upgrades..which in turn impacts all other ships that can take those upgrades (which may or may not be a bad thing) or increasing the point cost of the ship, which might not be efficient due to the ships base stats.
I'm not saying you have to say "You can only run 1 Y-Wing" but FFG could restrict it to an okay number for each ship chassis. I mean, imagine if there was a ship that was overpriced, but by reducing its points you could run more of that one type of ship. It would be a way of properly pricing a ship while not permitting a spam.
As for the discussion "Well, should someone be able to run X number of ships." It comes down to balance. I wouldn't go so far as restricting it down to one large base ship per list, but I'd at least stop someone flying something that could be oppressive at a fair points cost for one ship.