Can you explain why editing an ini or using the console command is not acceptable?
A big chunk of games I play also enter fullscreen mode when run, but only because the game’s config ini files have that config set. Don’t you just update the games ini files and ship it with that config? Just as many games also actually launch in a windowed mode, but then switch to fullscreen.
If you cannot use those 2 methods for whatever reason, can you explain your situation and offer an example of what you do need.