Many video games already do this with all the proprietary middleware they use (Bink, SpeedTree, PhysX, etc). Most launchers (Steam, GOG, Epic, etc) also require their respective .DLLs. Many games also use D3D11On12. Many shipping games in my list have dxil.dll amongst their installed files.
Therefore, an honest question: what's the problem with shipping an additional DLL? The work done here to reverse-engineer and re-implement the code-signing is fantastic—especially the fact that it is bitwise equal to dxil.dll's output. But I am ridiculously lazy and prefer to take the easier way out, and would've just shipped the DLL.