Porting an Open-Source Engine to the iPhone?

Evaluated several open source engines:

• Ogre: the architecture and design is not very performance friendly. The usage of C++ makes the usage and re-design here quite difficult. An example: each material has its own C++ file and there is an inheritance chain from a base class ...
• Irrlicht: the Mac OS X version I tried looks like a Quake 3 engine. It also seems to lack lots of design elements of a modern 3D engine. Other than this it looks quite good for a portable device. You might also use the original Quake 3 engine then ...
• Quake 3: this is obviously a very efficient game engine with rock-solid tools, I worked with this engine in the Medal of Honor series before, but I wanted a bit more flexibility and I wanted to target more advanced hardware.
• Crystal Space: why is everything a plug-in? Can't get my head around this.
• C4: this is one of my favourite engines, but it is closed source :-(

So I want to write my own based on the low-level framework I have in place now.