sp614x/optifine#3816 (comment), in 1.7.10 block.properties is loaded before forge is loaded, due to which all blocks from mods specified there are not loaded, like: [OptiFine] Shaders: Block not found for name: modname:block.
In my opinion, the load order can hardly be changed using mixins, so what if you try to reload the current shaders as soon as the forge loads? (this will most likely slow down the loading of the main menu, but this can be done as an option in the config that is turned off by default, so nothing will happen to those who play without shaders)

It seems unnecessary here, since Blendtronic seems to fix the problem (most likely optiFineShaderMappingFix?)