I have done plugins and pseudo loader for OpenSceneGraph to work with OpenGL es 2.0 spec and webgl. The first thing you need when working with big mesh is to split them in bunch of 65536 vertexes because opengl es 2.0 speccification limit the size of indexes to 16 bits. In order to manage this case, I have done a pseudo loader called split, so you can use it like that
osgconv hugemodel.osg.split hugemodel_splited.osg # careful about the MERGE_GEOMETRY flag in OSG_OPTIMIZATION
I have also done a resolve pseudo loading to re affect location of texture filename. The problem is that when I convert models to osgjs, osg is able to find the file because he can find in a path list, but once the image loaded it does not update the file location ( and it makes sense ) . It's not suitable for showwebgl that converts models on server side and need to reassign the image path before converting it to osgjs, this plugin loader is called resolve . And the last plugin is osgjs itself that is able to convert osg native format to osgjs format.