Ability to turn off features in Cycles for Faster Renders

There are times where I would like to be able to output just the Diffuse Colour Pass and AO pass and it has to work so hard just to render everything so perfectly when all I need is the Flat diffuse colour pass, which  I then have to seperate from the final render and I didnt neeed the rest. 

If not that, how about Cycles shaders that are similar to Mayas Surface shaders to make for a lighter scene,

 

Even if I turn off the combine pass it renders that pass,

As much as I know the BI render is better suited for shaderless rendering to get that flat vector look I don’t see why even if I turn off the Combine pass in Cycles it renders it anyway just so I can get the colour pass. It’s okay for simple scenes but then the scene is super complex it can take ages to render that Combine pass just so i can get that simple colour pass.

I know Cycles is made for more realistic things i feel having a fast shaderless pass without having to render out everything first would help.

for example what if i decided i needed a mask for a character I would need to render out that super slow combine pass which i had already rendered and now forced to render again, when all i need is a colour pass or ID pass of some kind, but i can’t render out just one pass without rendering alll the passes.

I have attached photos to show what I mean. the only pass that is turned on is the Diff col yet I have to wait for it to render everything first before i even get to see that pass.

Hope this makes sense.