So was insipred by Dj's idea and decided to make a improved version (wether it is improved i will leave youlot to decide lol).
As you can see theres no way for enemy to see you in your base.
Still the enemy can't see you in the base lol.
The built in crawl tunnel is hell on earth for the enemy lol, not only can you see them clear as day, but they have no way to shortcut by jumping up

, also the bunker slit is optional but i think it would be a good idea to use 2 at minimum on a full scale wall.
If you drop the flag in the crawl tunnel the enemy has no way to get it back from outside the tunnel.
Creation tutorial
Heres a really fast yet simple way to make this wall all by your self with no extra blocks that the ones you will use.
Step 1
Take your 1x5 and line it up at roughly the angle you want the wall to be at like so (don't worry about it being stright, you just want to get the angle for now).
Step 2
Go round to the front of the previously placed block and crawl as far upto the sf logo as possible :P
Unfreeze the block and let it fall down to the ground but do not move, your head will keep the block at the same angle, then refreez (now you can move the block to where you want it, then redo step 2 if it gets a bit messy looking with gaps at the bottom).
Step 3
Use the block in step 1&2 as a guide to place the next 1x5 ontop like so
Then pickup the 1x5 fromt he centre and walk round to the front of the block to place it at the front to make your crawl tunnel/bunker bottom.
Step 4
Repeat step 3 and place the block above the step 3 block
Voila a fast wall, crawl tunnel and bunker in under 40 seconds

(although if you make in in uder 40 seconds it looks no where as nice as the first images i posted, it tends to get a little bit wonkey, but still useable. With 12 blocks you can cover the length of skywalk easy, plus 2 for side swipes and you will have 16 spare to do with as you wish

).