In the game, as in real-life, the A330 and A340 share the same assembly line. The 757/767/777 do not, their final assembly is separate and therefore orders of one do not block orders of the other.
You will probably not get them separated, nor will you get more aircraft on the Used market. But what Sami may, and probably should, consider doing is allowing a greater variation in the dynamic production scheduling. For whatever reason it's reacting in the near-term, but not changing anymore beyond that. In 3 months time it's increasing production almost every month. Then it does nothing, even while the queue continues to lengthen.
You probably can't expect queues to not be terribly much shorter than 2-3 years though on popular planes. That's still a major concession over reality (and previous AWS games before dynamic production came into play in 1.1) where waits can be 2-3 times that long. This is an almost 30 year game. A wait of 3 years is a mere 10% of game-time. If you're struggling to get planes quickly, so are your competitors. Unless they have chosen alternate aircraft options, in which case you should too. That's an extremely important dynamic of reality (particulary in this particular time-frame that we are currently in, when air-traffic was booming but order queues at Boeing and Airbus just got longer and longer) that should be, and is, accurately reflected here.