Thanks for sending this! Rereading the documentation I see there is an easy way to have appropriate w10/w11 icons applied (although not dual-color icons of win11 as I still don't see the appropriate accent part of icon as a separate glyph). I'll do that in the next update.
Thanks for the offer on icons8. I'll have to read the terms there, but I will also need to see what would be the best way to support those. My original idea was to just build an font (seems to be an option for icons8) with the same unicode map as the segoe symbol font (so replacing copy icon would consist of adding a new icons8 icon in unicode position for original segoe icon for copy). Having those as fonts would have the benefit of being vectors and rendering well for all resolutions and no need to convert svgs to xaml, which is a painful process in InkScape, but would also have the benefit of cleartype rendering (not 100% sure), plus is the easiest to implement. That process of building a font is probably too complicated for end-users, but I am not aware that any user is even taking advantage of current way of swapping folder/file/menu icon replacements with PNGs, so it probably is not benefiting much to have those open to users as well.
I'll start with this swap with Fluent icons font for win11 and then later see what can be done with Icons8 and if they have everything needed in consistent look.