Well, since you ask....
Would you mind elaborating on and illustrating the points above?
Sure. Hopefully this helps.
Say a Heroic Tier Fighter and his allies are sitting on one side of a rectangular table while their opposition are sitting on the other with a couple of mooks standing behind them. Lets say a Social Skill Challenge has just ended in failure (negotiation breakdown or something) and suddenly chairs are being shoved back and weapons are being drawn.
The player of the Fighter says "I roar and grab the underside of the table and flip it on them!"
Alright.
1) So Heroic Tier and lets say the Limited Damage Expression you're using equals 20 damage total.
2) We go with Athletics High DC (I typically go there with Limited Use Expressions and Medium for At-Wills).
3) We discuss failure and go with a simple one. If the PC fails Athletics check, he gives up Combat Advantage UEoYNT.
4) The implementation will be:
a) Blast 3. Normal AoE, so we step back 5 damage from the budget (25% of 20 = 5). Now we're at 15.
b) Prone rider. Normal rider for a limited use effect in this tier of play. Step back 25 % again so now we're at 10.
c) Half Damage on miss. Half damage on a control-based attack (AoE + control rider) is pretty insignificant. If we were putting a control rider on this on a miss (like Slowed), then I'd step it back a full 12.5 % for a -2 to final damage expression. However, I'm only going to go with 1 in this case. So now we're at 9.
d) Difficult Terrain in that Blast 3. If you feel this gives the PCs a significant advantage in the scenario, then step it down a full 12.5 %. If you don't feel it gives a real advantage and just changes the battlefieldt, then leave it at 9. I feel it gives some advantage to the PCs, so I'm just going to step it down one to 8.
So we end up with:
TURN THE TABLE(S...)! Limited Use Terrain
Standard Action - Creatures in Blast 3
Skill: Athletics Hard DC (or give up CA UEoYNT).
Attack: Level + 3 vs Reflex
Damage: 1d10 +2 and prone.
Miss: Half damage
Effect: Blast 3 is DT.