Patching the binary isn’t an attractive option, but patching the Inform 6 that’s the output of the Inform 7 compiler isn’t so bad.
An alternative could be to put all your customizations into an extension, something like…
Bespoke Text by Mathew Plover begins here.
Xyzzy is always "plugh".
Bespoke text ends here.
Put that in dir1/Extensions/Mathew Plover/Bespoke Text.i7x, located someplace that isn’t within your project’s .inform or .materials directories. Placing dir1 as a sibling directory alongside them might be convenient, if that’s so, you could then compile your code manually at the command-line with:
inform7 --nest dir1 --project proj.inform
inform6 -wE2SDG proj.inform/Build/auto.inf dir1/output.ulx
(A previous brief description of compiling on the command-line.)
Then create dir2/Extensions/Mathew Plover/Bespoke Text.i7x with different values specified and repeat as necessary and automate the building with a makefile or something.