Here is a line of explorer yachts that has developed over a few designs (and about 10 years) but I think they're worth a study. The 62-meter was developed in 2001, a classic looking split level boat with the capacity to carry large tenders. This was commissioned for an existing client.
The 56-meter was an offshoot of this where our client really liked the general arrangement but the styling was modernized and the boat was made slightly more compact. The boat still maintains a very commercial look. Click here to access the blog posting about this boat and to see general arrangement plan.
And here is a much larger version at 82-meters. The styling was developed into more of a luxury yacht look with bigger eyebrows and "Euro" transom.
Here are the designer's comments. Please double click for zoom.