Okay, there is a random door in Littleroot Town, 2 in Pallet and 1 in Route 104.
We could have Team Magma attacking Silph Co? Or you could make a special hole in Victory Road which could lead to TM's base. Maxie could be at the end.
How is Team Magma going then? If we have done that, then we should have finished the main release. Also don't forget to remove the debug doors...
So all we need to do is add a "Locked" sign on Mr. Brineys door and we should be done for Hoenn... :)