It is possible but only g3d, z3d will be overridden by other shaders.
This however has more impact on performance than desktop use and you will need the vr hacked reshade dll to use (I only know reshade works, though there was vr enb for skyrim)
As for d3d9 conflict sometimes vorpx complains about it but works, sometimes it makes a game crash, sometimes you are able to rename it to any other dll to work. There is a list of dll names that windows applications load by default and with these post effect tools you can use those to make game hook post fx tool while not having vorpx complain.
All in all you have to try it yourself and success can vary per application and your dedication on trying to make it work.
I would really love to see Ralf incorporate full ReShade compatibility directly into vorpX. It would be so, vastly helpful.
I would think the way to do it would be to work with Crosire to implement ReShade within vorpX itself; you could install ReShade to vorpX itself and then within the vorpX control panel decide which specific shaders you want to push to any specific game title. It could really fix some issues. For one thing, you could turn off that damn TAA that soooooooo many games now use by default and use a ReShade AA method instead. That alone would make it worthwhile.
Alternatively Ralf could implement some more filters of his own directly. I would suggest that the most important item would be AA, so when we disable that in games we have an alternative. Other than that I would like to see Film Grain, as I often use that for immersion and it definitely can help to mask Z3D artifacts somewhat.