It'd be better if you said WHY it's a terrible idea.

Personally I'm in favor of this idea, and for a few different reasons. The one being there is less of "shopping list" feel to raiding.

Right now in order to stay "competitive" you need to do the following: VoA10, VoA25, Random Daily, Random Weekly, hit ToC10 and 25 for that damn trinket that wont drop, ICC10 and finally ICC25.

That's 8 different "to-do" items. Now, give the 10s and 25s the same gear (but make 25s slightly more attractive) and you get this:
VoA25, Random Daily, Random Weekly, ToC25 and ICC25.

Now we're down to only 5 items for the evening's list. (assuming you do it all in one fel swoop.) Pretty soon you'd get that trinket from ToC25 (since there are more drops proportionally) and you've filled out your badge gear comfortably. It then drops down to:
Maybe a quick VoA25, Random Daily, maybe the weekly, and ICC25.


You've picked up the same gear, but you've just cut the time investment in half. Why is that such a terrible idea?



Additionally, I think people are focusing on the "same gear" and missing the "more lucrative" bit. From what I've read I'm assuming the following hypothetical situation:
In 10s, ~2 pieces of gear and 1 badge drop. (and gold)
In 25s ~6 pieces of gear drop and 2 badges. (and gold)
Sure, it's the same gear. But in 10s it's a 1:5 and in 25s its a 1:4 ratio. Not to mention more badges for the effort.

If those are your only two options for a dungeon the logical choice would be to try for a 25 over the 10. THAT is what I understand "more lucrative to be"