Are you generating the configs for all these apps? Having a method of turning a universal theme spec into specific app configs might be worth more than the theme itself.
I got things set up to where I can run: set-theme gruvbox or set-theme one and it'll switch color themes in half a dozen apps. It also supports an optional --toggle-bg flag to flip between dark and light mode if the theme supports it.
Ended up being a fairly small zero dependency Python script that I put together in a few hours. I made a video about it here https://nickjanetakis.com/blog/a-terminal-tmux-vim-and-fzf-t... and the script is in my dotfiles at https://github.com/nickjj/dotfiles/blob/master/.local/bin/se....
But it wouldn't be hard to make the script more general purpose and put the configuration in a YAML file instead of in the script. Then add attributes for each supported app along with how those values would get replaced. If the app supports plain text config files it could realistically be done.