Although making an R.M.S (not H.M.T) Olympic wouldn't be much different than Titanic, since they were near identical sister ships, besides the open B-deck and post-Titanic she would have sixty-eight lifeboats. Britannic is another story, she had many modifications such as an enclosed aft well deck, many many more lifeboats, catwalk, and boat support around the electric gantry davit-based lifeboats, and most of her stern was different than the two sisters. It would be very difficult to produce a Britannic model without proper plans. You can get 3d printed Britannic parts from model shipways for scale model kits, but building from scratch with all the details would be almost impossible. Although I do wish that I had gotten Bob's plans before discontinuation, as they are very accurate and have everything you would need to build the ship.