I have the same problem.
I would discount the usefulness of the rotary rack. It wastes a lot of space in the corners of the safe.
I bought a big safe a number of years ago. The provided interior was attractive, well assembled, exactly as the picture in the catalog showed and nearly useless. Essentially too much wasted space.
My solution is two vertical racks for long guns, one in the rear (not as easy to use) and one in front for the more commonly used arms. I figured how much space the long guns took, added several inches to allow getting them in and out, and then arranged shelves above for handguns, scopes, magazines and anything else I figured needed locking up.
I started with 1x2 inch hardwood uprights in the corners and added cross bars as needed. I also put in fore and aft cross bars to support the horizontal supports for the long arms. By the way, I had to figure out what I wanted and then assemble the frame inside the safe; no way to build it outside and then put it in.
I don't have plans - and as I'm still recovering from moving, I don't even have a proper picture.
Note to others: When buying a gun safe, consider the option of NOT having an interior supplied. I don't think they ever quite fit. As usual, your mileage may vary, you're all big kids and the secretariat disavows all knowledge.