Apply RTpatches (or "Can we work around graphical setups?")
Patches created with RTPatch (https://www.pocketsoft.com/rtpatch_binary_diff_games.html) are difficult to apply at build time: it seems that they require a display just to ask the user to press "OK" :( But the Guix builder runs in a container without graphical access.
Ideally there would be a switch to run the patch silently, but I can't find it.
Example games include Command & Conquer: Generals.