I’m not sure that it’s neither possible nor desirable from a user POV. If I understand your idea properly, installing your package would make every other commands unavailable from the palette. Quite intrusive, isn’t it?
The command palette already filter the entries as you type, so if you use the package name as prefix it should reduce the suggested commands to the ones of your packages.
Now if you really want to have a command palette specifically for your package you can create your own view based on the original one and binds it to a different keybinding:
The code is quite simple so it shouldn’t be much work to adapt it to your need.