While on a wall...
Some people may argue that no, it would make it too powerful. Well then, why can you shoot bursts or bouncers off of walls? You could also just take it out of your level.
My thinking is that currently people add them in for fun or just a filler. However, this could be a real gameplay option, an addition to the defensive features.
Remember that one way wall a while back? They go arm in arm together. Instead of using a portal to get onto the wall, players could just walk up onto the wall and defend.
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EDIT Oct. 2011: I still like the idea of a one way wall -- being able to fly up onto a wall and have temporary protection from enemies or safely move to another area. And the idea of using one way walls as a method of defense was a neat idea.
However, being able to shoot off the end seems extremely unfair. Players could fire phasers off the edge at enemies and be completely protected from damage. It would really depend on how the level editor utilized these one way walls.
As for the current set-up:
If possible, the glitch allowing bouncers to shoot past the wall should be removed. I don't know about bursts, as they're not as accurate, but bouncers escaping the wall barrier should definitely be disabled.