That is a good idea Wolf Knight,
but not entirely the best it could be.
The attackers could easily just bash through the lower wall
And run right under the defenders,
Even attacking them from behind.
Then while the defenders are pushed against the wall with nowhere to go
It becomes a blood bath for the defenders as opposed to the attackers.
To maxamise the effectiveness of this idea
There should be solid wall pieces to support the second wall pieces.
(just a small adjustment)
Also, to strengthen the gate...
Make a corridor between the first gate and a second gate,
Make it 2 units wide and 2 units long using these pieces:
30 07 0780 - Floor, 1x2 units, square holeThen while the attackers are trying to knock through the second gate,
Pour boiling oil on them as they work...
Also, putting arrow slits in the walls on either side of the corridor
Allows archers to shoot at the attackers while the burning oil takes it's toll.
Another thing you can do to help strengthen the walls is to put small outlets
Maybe one or two steck sections out from the walls every foot and a half.
Make them into towers if you want,
But that is not really necessary.
These outlets can be used to fire on the backs of the besiegers (using archers)
while they climb/attack the wall.
The outlets should be small enough that they can only be attacked by small bands of men at a time, thus allowing your men stationed there to fight them off easily enough.
That is all I can think of for now,
Hope it helps.