applications - How to mod android rom so none can ever install an app in it?

I already know how to modify an android ROM by modifying files, remove and add it into ROM. But I don't have knowledge to building/compiling a ROM.

I want to lock the OS so none can ever install new app to it. Well at least for they that not have a knowledge to flash the ROM with other OS.

Is there a way to prevent user from install any application to the ROM?

like removing the market app or the package installer, pros n cons?