If you're NOT writing a web browser, and the little voice in your head says something like "I know! I'll solve that by writing a plug-in system and let other developers write to my API, and all their code will run in a sandbox, and I'll write a virtual filesystem for them to use, and I'll provide an installation/uninstallation system, and maybe a debugger..."

STOP

Get up and walk away from the keyboard for a bit. Maybe take a refreshing shower. Clear your head and let yourself think this through a bit. You'll come to the right conclusion. Now go back to your keyboard and work on something that delivers value for your customers :)