Hey unska, <img src="{SMILIES_PATH}/icon_e_smile.gif" alt=":)" title="Smile">
Construct 2 has a feature called "Families" which might help out in this case.
Manual > Families: https://www.scirra.com/manual/142/families
You can put several objects in a family, then write events that apply to the family , and those events will affect all the family member objects.
You can also add private variables to a family, and all family member objects will get their own local copies of those variables. This could be handy for the properties common to all monsters, speed, bullets, health, sprite, name, loot drop, and such.
As for collisions and graphics, for a single character I usually create two separate dedicated objects. One for collisions, physics, and motion, and one for the graphical representation of the object in the game. The physics object will be invisible. The graphics object will be pinned to the physics object. This way my collision geometry can be very simple and predictable, and my graphics can be modified without affecting the collision properties of the character.