Greetings, chickentwisty!
Closest add-on that can be useful for your goals is our Shipping and Payment Restrictions add-on.
However, there is no quantity selected restriction there, this could be possibly added as a modification.
But if take into accout that different products can have really large weight and volume difference, I believe you can work it out by simply setting restrictions on a product level, e.g. for products with large weight and/or volume value you can ONLY allow shipping method C. If you feel the idea, this could provide a quite good approximation. But in order to make it work precisely, as you said:
We had a client with a similar request and you are correct, this task is not trivial at all and is pretty expensive.
Once again, we are not claiming that our add-on covers everything that you described, but we do recommend to at least take a look at it, check the Docs as this solution is possibly the closest one to your needs.
Please feel free to ask any questions.
Best regards,
Cart-Power