Can the cargo module be used as an improvised hangar, and can one use tractor beams to pull the Tumbril Nova or Atlas-platform vehicles into the cargo module?

If you can fit the vehicle either through the door to the hangar or up the lift then this is perfectly possible… but not intended! The cargo lift is capable of loading two 32 SCU containers at a time, so vehicles up to and including the RSI Ursa will comfortably fit.