In order to drop the object, he must either have his Super Strength Outwitted or lose it through taking damage. Since he has Super Strength down the dial, that only leaves Outwit. So I'd just recommend you don't Outwit his Super Strength up there, especially since you have more to fear from his regular ranged attack than you do from an object's ranged attack.

If he manages to get up there on top of an object, he will as always be unhittable by ranged combat for that first Stealth cilck. The only way to hit him will be for him to turn off his Stealth, or for a figure with flight/LC to get up on top of the same EBT and use close combat, or to destroy the EBT. Or, of course, use some strategy to clear away the object. Note: A figure with LC cannot make close combat attacks unless he is on the same EBT.

Not doable, actually.

You're slightly misinterpreting. The vents and whatnot are elevated blocking terrain, per the FAQ, and are therefore elevated. What DrG was almost surely saying was that they do not constitute another level of elevation. They are blocking terrain on a rooftop; they are the same elevation as the rest of the rooftop.

What's this in reference to?

That's why I'm saying that the ruling is inconsistent.

You'd never have a case where something on the 'grounded' level or on an Indoor map was surrounded by thick black lines and then not considered to be blocking terrain for the purposes of line of fire from other people on the same elevation.

Can you place a object on a 'air conditioner,' during your initial set-up of placing your items on the map?

Which is why this is an exception, and was given a rather sizable FAQ entry. Feel free to call it inconsistent with the rulebook definitions; that's why the entry was needed.

HeroComplex said "In order to drop the object, he must either have his Super Strength Outwitted or lose it through taking damage. Since he has Super Strength down the dial, that only leaves Outwit. So I'd just recommend you don't Outwit his Super Strength up there, especially since you have more to fear from his regular ranged attack than you do from an object's ranged attack."

Hate to add a new twist...I do believe you can personally turn off your superstrength...like you can turn off your stealth. The faq's say that it is an optional power. And, since MM has stealth...you can't outwit any of his other powers has long as he is in hindering terrain.

It's actually the PAC which says that Super Strength is optional. The FAQ has something very different to say:
Once you pick up the object, you're stuck with it until either you use it, or your opponent Outwits the power.

Which, of course, isn't the case until the object is dropped under him. Which won't be the case until he is Outwitted.

From the FAQ:
"If character with Super Strength is carrying an object, that character's Super Strength power is not optional (it cannot voluntarily be "turned off", but it may still be outwitted)."

So you can't have MM turn off his super strength while holding an object.