For Arcane sword, it's just easier to say it goes to the body. If you say the square they dies in, the body might not be there. It could be taken away, fall/ pushes off a cliff, into a pit ect. That way, you might be alive but in the bottom of a pit when you wake up.
An far as NO body, lava and acid can quickly take care of a body, normal fire can leave ashes, a large block could leave you a fine paste, ect. Plenty of ways there is no body left.
As far as Total Aegis, you may be right. Until then however, the epic utility is the only way Ensnarement gets a Total Aegis like ability. Add to that the fact that most feats of this level are pretty darn good, being able to use a utility instead of a feat isn't a bad deal.
For Feyliege, you want to go back to your less regal form for you can use that power again. If you are already the older version, it can't come save you again can it?
As far as the body disappearing, It sounds like the older version replaces it. EI it becomes the older version. So when it reverts to the 'original', if there is a body it comes back to life. If it's NOT, then you stay as your older self. At least that's how it reads to me.
I don't worry too much over word polish. You can ALWAYS word something better. And they didn't make any clear loopholes, so I can't complain.