Hey AGS if you really want to test and market this game engine, you should take a shot at making Sea Ships and boats and seeing how well that runs on a large scale.
A lot of physics involved and also performance testing for larger water bodies.
Also a Large Scale PvPvE zone that concentrates large groups of players into the same areas to fight, would really test how well the engine holds up with large number of players, which is essential to future Large Scale PvP MMOs.