There is requests for substance material support. And I would like to have procediral maps in material editor (tile/noise/dirt...) like in other renderers. And sure it is cool to have more than one layer per map slot. There could be blending mode (multyplay/exclude/screen...) for map layers.
And another feature: why is there slider brightness? it makes the same as Amount as I see. Slider "levels" or "curves" or "GAMMA" would be here more useful..., to transform diffmap to bumpmap for example.