If you want an interior of the U-99, watch the movie "Das Boot", it has AWESOME interior shots, and it also shows how resource intensive something like that would be.  You not only have food, you have the various compartments, bulkheads, doors, etc.

If you want these poseable, it may be too resource intensive, but could probably be done. If you want interior props where you could focus on a section, then it may not be bad.

If anyone DOES want to try this, I would strongly recommend watching "Das Boot", it shows every section of the submarine, and basically how it was laid out.