Grim, please explain better how this stage can't be circlecamped. I could easily jump over the **** you throw at me while I run away.
I'll edit this post with a diagram in a moment.
EDIT:
This by no means works for every character, but there are many MUs which can get camped anyway (Wario vs. Lucario, Ganon vs. pretty much everyone, etc...)
You could also place another hazard somewhere as well, but that is about all you need as most characters.
Preferably upgrade the hazards for extra speed, priority, etc... (Fox Illusion is stopped by every hazard iirc).
If you need extra time, you can place the hazards so they walk down to the correct area.
Pretty much all of the high tiers have a method of stopping it, which is all that really matters.
Meta Knight has... Well, he's Meta Knight xD
Snake has Nades, C4 and Mines.
Diddy has Nanas.
Wario has aerial speed.
Falco has lasers.
Dedede has Waddle Dees (I know...).
Marth might have a bit of a problem... But eh. He can probably stop it with persistence.
You can also wait for the flame to interrupt the circle if you want to be extra cautious, but I don't recommend it.
EDIT2: Alternate Method:
The bottom hazard could theoretically be on either side.
By "camp POW block" I mean de-activating the top hazard until you need it. As it is difficult to control from that position.
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Also note that the cramped space makes it more difficult to avoid hazards than you'd first expect, and that many players can shark through the platforms to aid the afore-mentioned strats.