If you don't change the model correctly it won't work right because some parts won't have the right collision.
So one shall change the model then, more or less..
What I care more of is what it's seen, and how I can place the bricks. I want to make a wall out of those, that's what I want to do.
Something like

Just imagine the red parts are holes, and that they are bigger...
That's what I want to do out of those.