I were removing pre-installed programs yesterday in a virtual machine, meta-packages as stated by @rohithmadhavan are perfectly safe to "remove".
ubuntu-mate-desktop
ubuntu-mate-core
mate-core
There were clarification about swapping LibreOffice in another thread:
In summary, meta-packages act like a list telling it which other packages to install. Since you remove one of them, this effectively means we don't need that "list" anymore.