You've talked of sonobouy carriage, but what about weapons? Unless you hang an awful lot of pylons on the wing you will need a bomb bay - which will raise the height of the floor. You will also need to be able to load/rerole the bomb bay quickly, which means being able to get trolleys and tractors underneath - unless you're thinking WW2 and pushing them underneath by hand - as well as providing working room for the armourers, so possibly a longer undercarriage.
(And a couple of turret mounted 20mm cannon at the front for the pilots to play with!
)