This very nice desktop OpenGL has been ratified as a OpenGL ES extension recently.
I would like to request support for this extension since it will improve performance of my application by a very large margin on Mali hardware.
It's at the Khronos registry here. https://www.khronos.org/registry/gles/extensions/EXT/EXT_draw_elements_base_vertex.txt
With this extension we are able to use the elements buffer as a ring buffer, updating portions of it as we go making sure to never trample GPU state as we go along.
Due to the nature of our application, we have many many updates that we have to push through the elements buffer, and without this extension it is the most inefficient for us.
Do you know what your "inefficiency" actually is? It's still not clear to me what the specific bottleneck your application is hitting (CPU load for binding, attribute setting, memory upload of index buffer data, etc).
If the overhead is index upload for new indices via glBufferSubData, what is stopping you using an existing "in memory" index buffer, and providing appropriately modified data offsets into glVertexAttribPointer per drawcall?
All this extension really provides is a cleaner interface to avoid the need for blatant "hacky" offset mangling in the application, but the ability to set an arbitrary offset in to a VBO already there today, and shouldn't actually be that expensive.