The Charge rules leave a lot to be desired. For one, I agree that it seems you could run around something blocking the path (other fighters, terrain, etc.) but I don't think you could, for example, take a wide arcing route just to allow yourself to Engage from outside the defender's vision arc to get the benefits of Backstabbing. (I don't know, maybe you can...) But why would that be any different?
Another thing I think is unclear is that the 1" rule says you can only pass within 1" of an enemy fighters if making a Charge action AND you end-up in B2B contact with an enemy fighter. So, take Example 1 above. If the Charging fighter fails to reach the enemy in the back row, then, by RAW, he would not be allowed to pass within 1" of the fighters in the front row. So, does he have to stop at the fighters in the front row? But shouldn't his Charge action be able to take him between the front fighters and leave him in the open space between the rows of enemy fighters?
The rules don't support this, but I think it would be better if you had to declare a target of the Charge and the path you are going to take. For one, if allowing the fighter to pick a different target after rolling the die and finding out that he doesn't have enough range to get there, that's equivalent of pre-measuring.
One thing I do think is clear is the Versatile thing. Charge says you get a free Fight action if you are Engaged at the end of the Move. Versatile says you are Engaged if, during your activation, you are within the range of the weapon. So even if your Charge falls short of B2B, if you are within range of your Versatile weapon you are definitely Engaged and entitled to a free fight action. GW doesn't get much more unambiguous than that.