I had a thought of the use of the sarcophagus. This may have come up before, if so sorry.
My thought was there is nothing wrong with them at all, no faults to fix.
My reasons. Its purpose is to heal. there are drugs and treatments known to us now that do good but can do damage if used when not needed. I feel the sarcophagus are the same. We see O'Neill put through god knows how many times and there is no apparent insanity. Daniel goes through a few times and starts to show signs of it. (Sorry I can't remember the episode names). The difference O'Neill was dead when he was inside, Daniel had no injuries (apart from the first time). So could it be that the sarcophagus only causes insanity when it is abused? The goa'uld certainly do so, as they use it to prolong there life.