Custom bootloader on pro micro for keyboard

Hi all,
just had a dumb though on bootloaders for my keyboard project and if it would be possible to make it so you cannot upload code to the Arduino. This is so I have my keyboard and I do not accidentally upload a new sketch to it.
just though it might be cool even if it was a mechanical/physical change it would feel more professional.

Why a "custom bootloader" instead of just omitting the bootloader entirely?