I would wall and plaster around the trunk to keep crawling things away, but keep the tree alive, then erect several concrete pillars all round to hold up the structure. Remove only the few branches that need to give space to the house, then build everything else with wood. You can roof with makuti and paint the roof green. It would be nice to have a balcony and windows peeking out of the foliage. Be sure to keep a cat; it will keep small bothersome things like snakes and geckos away.