I also pointed the last command of Steam version to TQ.exe instead of steam://rungameid/475150, in order to start with the launcher if I want to choose between DX9 and DX11.
When I did that, it gave me an error message (files corrupted). I don't know why.
I've noticed an issue with the icon switch (mispelling in ui_loadingart_grey01, should be ui_loadingartgrey_01). EDIT : fixed in v3.
Correct code would be
Play SV
REN ui_loadingart_01.tex ui_loadingart_01_vanilla.tex
REN ui_loadingart_01_soulvizier.tex ui_loadingart_01.tex
REN ui_loadingart_grey01.tex ui_loadingart_grey01_vanilla.tex
REN ui_loadingart_grey01_soulvizier.tex ui_loadingart_grey01.tex
Play vanilla
REN ui_loadingart_01.tex ui_loadingart_01_soulvizier.tex
REN ui_loadingart_01_vanilla.tex ui_loadingart_01.tex
REN ui_loadingart_grey01.tex ui_loadingart_grey01_soulvizier.tex
REN ui_loadingart_grey01_vanilla.tex ui_loadingart_grey01.tex
As for options and customization, I leave it for everyone to understand how this work and adapt it to their liking.