One point is that a new package, or a newer version of one, may require the update of a dependency, and that may trigger the update and compilation of a whole list of packages. I think that is aceptable, but should be a opt in. “Installing package Xxx requires updating N packages. Type D for detail’s. Continue? (Y/N)”.
Better yet if it was possible to suggest the latest version that could be installed without changing the current package state.