I had a similar though process, as far as something to make the walls closing in be more fun, and gave an example of one idea in my Arena Idea: Whirlpool thread.
Another idea I had for this was:
- Robots programmed to move in closer, charged with forcing the combatants to fight or kill them if they refuse. Attacking one would of, course, summon others. If you managed to kill one, which would be very difficult to say the least, you would have access to a awesome laser weapon with X amount of ammo that you could then use on other combatants. I have already argued the pros and cons of this particular idea, and admit perhaps it is best that they just have shields to make them immune to damage and if you get to close, die. I did amuse myself thinking about it though.
The problem is, for me, I would want to to know why something is closing in on an ever shrinking circle. Of course we know why the map is getting smaller, which is to force fighting, but what is the lore behind the chosen mechanic?
Example, by default we know that it is to make us fight. But why would a bunch of random crocodiles be slowly circling in on people who are trying to kill each other? It would be more interesting if they were cyborg crocodiles and the match type was a swamp in my opinion.(I may or may not have a partially written up idea for exactly that)
Long story short, I would personally want to know why a specific mechanic is closing in on us aside from the obvious. Example, I wanted to use some sort of blizzard as a particular mechanic but cannot think of any reason why a blizzard would slowly be closing in around an arena. Unless, of course, it was an artificial blizzard. Which would make an awesome arena for a Christmas special where you can run around killing people with giant candy canes, throwing ninja tree stars, ornament/snowball grenades, and running people over with reindeer. (Another arena idea I may or may not of had fun thinking about)
I guess the biggest questions would be would most people want a reasonable explanation for WHY the different variations happen or just accept that it is a form of a wall closing in constantly?