It's absolutely possible but no one is interested in doing the work to implement D3D8 right now. DXVK should work with D3D8to9 if you install Microsofts D3DX9. The Wine implementation is not good enough.
But honestly, we're talking about D3D8 games here. Just play those with WineD3D. It's not like performance is gonna be a big problem with those games anyway.
I tried to combine @crosire's d3d8to9 libraries to first convert Dx8 to Dx9 then used your Dxvk to convert Dx9 to Vulkan, placed d3d8.dll and d3d9.dll to the same folder but game that i tried is crashed. Is it possible to Dxvk to handle Dx8 too please