Outboard vs. Inboard
Today''s outboards are better built and more reliable than they used to be. In some other sailing venue I would say that an outboard would be fine, But the area you are proposing to sail within is notorious for its chop and outboards are next to useless when things get really bouncy.
I do think that an inboard is better suited for a liveaboard. I don''t think it needs to be a diesel. Carefully maintained and used a gas engine can be quite safe and substantially less money to buy and maintain.