So now, one thing to do is to find a suitable way to "test" ship designs

My first reaction to "testing" warship designs was to look for a suitable set of existing rules, or, better yet, a computer naval wargame. The problem that I find PC games, is that they are necessarily "closed". You can't add ships to them, generally. Also, if it is 3D game, however simple, you need a 3D model. A good example of a low end 3D game is the Fighting Steel Project ((c) Naval Warfare Simulations). There are a number of difficulties surrounding computer games:

1. The cost and time involved in doing anything significant
2. The incompatibility between openness and the necessity to make money to stay afloat as a developer or company
3. The limits of current technology, which will not allow large numbers of ships to be used

One thing that we could use is a combination warship design/3D model building program that would produce models suitable for use in some open game system with production values equal to what the large companies can produce.