Bgfx sypports Direct3D 9 - 11, OpenGL 2.1 - 3.1, OpenGL ES 2 - 3. What do you think about this renderer? What about plugging it for the BGE renderer? If you use different renderer, does that mean the shaders will have to be rewritten, like bloom, will they be faster? Right now they are slow. Also does it mean, that bgfx will make possible to have android export?
So, yeah, I doubt you could just drop in your existing GLSL code.
There are a lot of different renderers out there, and a lot of them could be integrated, in theory, but it would still take a lot of work, and it might not be worth the effort.
As for android export - the renderer is just one part of the engine, so unless you can port everything, it doesn’t really matter.
You wrote 3 lines of text in a post. That took you how long?
Nobody even knows how much it needs to get another renderer applied to the BGE. Just to find that you have to investigate really much time. (The BGE is open source so feel free to do so)
Yes, the idea of plugable renderers sounds cool. Because there is an renderer already, you would have to pay for the coolness.
There were tries in the past to integrate ogre3d and crystal space. As far as I know this was not really successfully.