How to change scale of a gameobject using a vector3 variable.

In my game, the player collects monsters and uses them to battle, like pokemon. The gameObject I use as my player's monster has to change scale throughout the game, to accommodate the different sized monsters. I want my monster object to inherit all its attributes (health, attack, level, size, etc) from a single class (BaseMonsterClass). How can I get the scale and collider to change size whenever I select a new monster?