With ION the problem might be in the memory bandwidth that you have from GPU to system memory (vidoe frame needs to be copied and it is generally with all GPUs).
There are two ways that could be tried for reducing the GPU / CPU power requirements for the plugins that are analysing video frame's content.
1) Allow plugins to request lower resolution video frame textures from GPU (GPU would resize the video texture to lower resolution before it is transferred to system RAM)
2) Use pixel shaders to do the analysis in GPU space
Neither of those cannot be done without modifying the MP's source code.