yeah open source game contest is a great idea! (retro or not retro is another question) in general I prefer open source stuff, especially when the community has the right to use all of the assets freely in their games! (in general I find it a bad thing that the engine does not include any free-to-use up-to-date graphics assets, and sample games beside the templates)

tools would be also very useful thanks to the missing features of the engine, but they need more effort to implement, so they would probably need longer time to develop... (GUI, effect, shader, pathfinding/AI editors, or shader packages etc.)