This might sound like an insane question, but is the overall theme of 4e to say "yes" to everything, including things like the above bolded text? Something I was reading, (not sure now, everything is a blur in the crash course) that you should try to say yes, (like Jim Carey in "Yes Man") to everything and find a creative way to make it work. If a power doesn't fit the creature, I would think saying "no" would be correct, like the ooze and the leg sweep power.
Say Yes to everything is more or less the theme, yes. And remember that many monsters will have some rules surrounding what does and does not work on them which attempt to simulate aspects of their powerset or physiology. Elemental creatures are all resistant or immune to the relevent element. Undead laugh at poison. Some tough creatures can't be knocked prone, and others can resist being slowed or forced to move.
The thing is though is that these resistances tend to be fairly limited, and only to apply to a few powers. Part of this is for bookkeeping (it can be hard to keep track when one monster has like 15 resistances and immunities), but its also for balance--its fine when a character is made slightly less effective against a certain kind of monster (say, because that character has a lot of forced movement powers, and the monster is resistant to that). Its less fun when none of a character's powers work, and he's essentially rendered ineffective throughout the fight. 4e mostly rejects the 3e paradigm of "oh you're a rogue facing some undead? tough luck, you're screwed."
In fact, I was thinking one encounter might be a "anti-arcane" zone in a dungeon where arcane powers don't work, or "anti-martial arena" where combatants duke it out, toe to toe, mano-y-mano, with basic attacks and wits and martial powers cannot function.
Anti-magic zones in previous editions were primarily a clumsy balancing mechanism to compensate for the dominance of casters at high levels. The caster would kick ass 90% of the time, but every so often he'd hit some anti-magic, turn back into a schlub, and the fighter could dominate.
This isn't really the dynamic in 4e. Everything is balanced, and everyone is always contributing. You never have a fighter who becomes obsolete and needs to be made relevant again via anti-magic. He's always gonna be a badass who more than holds his own against the wizard.
So, think about why you want to include anti-powersource zones, what you're trying to accomplish. If it isn't for balance, then what does it add? Limiting characters can force them to think outside the box or come up with unorthodox solutions, but only to a point--antimagic that simply shuts off a wizard's powers completely is instead more likely to simply frustrate them and make them more or less a non-factor for that encounter.
If you want to throw some wrinkles at your players and make them sweat a little (and what DM doesn't), 4e offers lots of ways to do so without simply shutting off their powers. Build encounters to counteract their strengths--if a mage always goes invisible, put 'em against a monster with true seeing and see how they handle it. If the strikers decimate even the strongest single targets, try a horde of minions and see how they like it when their massive attacks are mostly wasted, and the enemies just keep coming. If the party doesn't have a ton of range, put 'em against artillery or even some flying enemies.
Generally, letting the characters keep their powers, but putting them in situations where those powers must be used creatively to win will be more fun for players than simply taking those powers away. If someone rolled a wizard, chances are they want to play a wizard. Antimagic turns them into a non-wizard for its duration.
