Transparency group pdf Xobjects

Hi pdftex team,

The current text transparency model used by latex (using fontspec  option
opacity or package transparent) is insufficient for a lot of scripts, and
fonts. It seems like the problem can be solved by either putting a
hbox/vbox (that contains text) into a pdf transparency group, or if that's
possible then by putting contents of package
textpos's environment textblock (which has a known absolute location in
pdf) into transparency group. I read pdftex about  manual's interface
`\pdfxform`, though I did not understand it enough to be able to use it.
Can someone please help? Here's the question posted on TeX.SE:
https://tex.stackexchange.com/q/565281/192717

Thanks!