it will not be a hard work to do
This is HARD WORK. Require to wrap all the Irrlicht functions, and the low level function in IRB to LUA. LUA is a scripting language and must be compiled on the fly. It's not that fast.
Currently LUA is not used in the main loop but only when the game start. So you would need to create a editor side support for LUA since you're talking of also adding features to the editor.
The focus of using LUA in IRB is to be used only on small, quick operation, and triggers based on events, so it hopefully it remain fast as the rest is in C++. Never to be used in the main render loop. What you would like to do, is make it all run from LUA, if somebody want to do it, I hope they know how to optimize applications because it will require it (probably will also need to switch to LUAJit)
There is this project that give you access to all Irrlicht functions from LUA if you want to see how it's working:http://irrlua.sourceforge.net/
As other alternatives, there is the LEADWERKS project (http://www.leadwerks.com/
) That allow you to do a lot of things from LUA (Much more than IRB)
NOTE: LIBGDX uses OPENGL ES, and can do 3D too, it's not limited to 2D only.