To be honest, you are not really trying to make an engine. When speaking of engines, most people refer to their own graphics engine, using some framework like ogre/irrlicht is already understood as engine, thought a game engine often included more like physics, scripting etc. you will have no trouble of adding existing libs for these tasks.
I'm open to suggestions of any kind, except ones that say: "Just give up on making an engine."
When it comes down to your requirement list I think that ogre/irrlicht are the only really popular options to choose from, everything else is already a game engines (UDK,CE,Unity). Btw. Unity is a popular cross-plattform engine, but maybe already too much for your requirements.