Hello! It's me, weee50! I have the skills of creating custom test chamber signs, like this!
Like these? They are custom Test Chambers 20, 21 and 22 signs.
Test Chamber 20 would be a test chamber which starts like Test Chamber 17, but generates a storage cube. Then there will be a turret fling section. When you fling the turret in, the turret will hit a button which opens a door. There will be a checkpoint once you go through it. Then there will be a metal parkour. At the last 3 blocks, Crushers will appear. At the last block, you will see the chamberlock. However, you need the cube to open it. (Once you see crushers, GLaDOS will say "These are crushers. Sorry we haven't put up a danger sign for them.")
Test Chamber 21 would be Advanced Test Chamber 17, only without GLaDOS's voice lines.
Test Chamber 22 would be Test Chamber 19 as it is currently.
NOTE: Test Chamber 19 (With these levels) would be the original Test Chamber 19 only instead of the ASUsS driving into the firepit, it drives into an elevator. (GLaDOS does not say his voice lines.)