I think it makes sense to switch to the DirectX 11 RenderSystem as the default RenderSystem in the near future as this is used by Win8/Metro also.
Basically the Feature Levels should work flawless even when using old cards.
Do you have a reference project that shows the described behaviour? Maybe you touched areas that need to be emulated in software as it is not supported by the intel chip? If you don't have a reference project, please tell us more about what you've done
and how you did measure the performance, because this may be a good hint if we need to maintain a DX9 RenderSystem or not.