Programmable blending for ios.

It would be very useful to get current pixel color when rendering translucent meshes on ios. On other platforms you can use scene color but this has obvious performance problems but on iOs you can get current pixel color to shader(all blending is done at shader at anyway on ios). This could be supported with Scene color node with restriction that you can plug any coordinates to that node on ios. This would allow to make materials like tinted glass or water on mobile.