This is trumped-up BS. You do have to pay about $10 for the charger. "You can't use the phone while you're charging" is just false if you buy a few batteries, as I suggested in the message you are responding to.
And why do you have to buy all those chargers and I don't? I find that one is plenty. Of course, paying another $10 or even $20 would be cheap.
As for the wear in opening the case, it's about as much of a problem as opening your refrigerator door. Actually, less.
I've been doing this with Nokia tablets for years without problems. How much experience do you have trying this solution? I suspect zero, judging from the objections you raised.