Think Imperial Knight mounted from the hips on a slightly shortened Baneblade. Maybe
can put a picture up with a reference model or two?
As for the Belly gun being funny... I've never really been a fan of the concept, though I'm glad this one's modeled with one of the less suggestive
guns. This one at least looks like a belly rahter than a... well, let's just agree the Stompa's version
is beyond saving.
Ask not the Eldar a question, for they will give you three answers; all of which are true and horrifying to know.