chest-high walls are simply the next-gen version of the crate ...
what we really need is exploding walls ... although that could be taken care of by destructable walls.
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Would? Dunno, UT4 seems pretty unlikely at this point, and if they did make it they'd probably just mess it up again... Should? Absolutely! UT would be a much more interesting game if it blended crazy, fastpaced arena action with GoW style tactical elements (among other things).
I'd say that something of that nature could put a UT-like shooter back in the higher rankings of the leaderboards.
It certainly would be an interesting experiment.
Of course the hardcore ut-players are unlikely to care about such things.
then again ... they are almost extinct as a breed, so it's not like we're going to miss them