your argument is invalid. you must think of the extremes of "the people are going to abuse it" argument
if at the beginning of the game you character has all the best weapons and armor for the game laid out right in front of him. He doesn't have to pick it up, but lots of players, especially newcomers to the series, will. having all the best weapons and armor at the very beginning would ruin a game like TES.
The same principles relate to overpowering enchanting. I don't think necesarrily it should be impossible to become overpowered with enchantments, but one should have to be a very high level to attain such powerful items. In Daggerfall, Morrowind and Oblivion, you could make these items at a very low level.
I don't recall saying that anything should be readily available at the beginning of the game (goes back and looks...) Nope. I didn't. You assumed totally for the sake of your own argument.
Since enchanting will be returning as a skill, no one would be able to enchant to 100% without a considerable amount of skill in enchanting. More likely than not, it would be Master level.
As far as paying to have something enchanted. The price would be steep considering the amount of skill it takes.
EDIT: This way, anyone can still enchant to 100% if they want, or they don't have to if they don't want to. All the while, the ability to enchant to 100% remains reserved for players who have put in a considerable amount of time to do so. Win/Win situation here.
Both of these prevent anyone from jumping into the game and instantly being invincible.
You don't know what any other players will do. Nor do I for that matter. Everything is assumed and you are assuming that everyone is suddenly going to abuse a system that you don't like. When I first played Morrowind (the first game I played in TES series) I had it on PC. I didn't instantly jump into the construction set to give myself all the best everything so I could be God, and I most certainly could have because the CS is wicked easy to use. So you're assumption that new players would abuse this system holds no water.
And furthermore, as I stated, the way one person plays the game, really doesn't affect anyone else. Just because you think it's a flaw because "OMG it MIGHT get abused!" doesn't mean it needs to be changed. If you don't want to use it, don't. It's honestly really easy and the game is set up so that anyone can play the way they want to play.