Automation Control Cabinet Isolation
From the safety perspective, it would be logical to disconnect all three phases with the main switch. Maintenance personnel would also expect/assume that it would be so.

Door-mounting of the main switch would only be an alternative to side-mounting without any added benefits. In fact, door-mounting would be more unsafe than side-mounting, considering the routing of the 10mm² cables with sufficient slack and the chances of exposure of personnel to live points.

A door-interlocked main switch would render the cabinet inherently safe and would also conform to safety norms worldwide (considering it as a product and not a one-off).

In my opinion, a door-interlocked main switch, to disconnect all three phases, would be the right choice. 

It would be worth your while to redo the layout.